the most intelligent and desirable combinations. To do this requires an intimate knowledge of the habits, adaptabilities and capabilities of each species, their congenialities and uncongenialities in combination with each other; the degree of resistance of each to diseases, cold and heat. Yet coming back to practical work we find the great simple law or rule of nature, that, in breeding, especially in pure breeding by selection alone "like produces like.' This must not be understood as identical, for no two are ever identically alike. Similarity is meant. What I mean by the law is that to produce black varieties plant seeds of black kinds (although seeds of red and white kinds sometimes produce black kinds and vice versa, showing that some progenitor bound up in the parent had the same color of the stray). To produce big clusters, plant seeds of big clustered kinds: some of the seedlings will bear larger clusters perhaps than the parent, save them. To produce big berries, plant seeds of big berried kinds: some of the progeny will perhaps have larger berries than the parent, save them. To get freedom from diseases, plant seeds of varieties. resistant to diseases. To get fine flavors the parents must have fine flaBut in making combination sometimes entirely new characters are produced and this gives a great bound in development and greatly hastens the work almost to an absolutely new creation. Especially is this the case with some new flavors in hybrids that the varieties of pure bloods do not possess, and never can for they alone never can make the chemical compounds that may occur in hybrid combinations. If I desire to produce sweeter or more acid kinds my taste is an unreliable guide, It will pronounce a variety very ordinary in sugar to be quite sweet if it is low in acid. Such is the Concord, one of the very lowest in sugar, also one of the lowest in acid. One of my hybrids which everyone in tasting declares "the sweetest grape I ever tasted" is really quite low in sugar and is almost entirely wanting in acid. To aid us at this point we must use the sacharometer and acidometer, two very delicate instruments for determining these points. Having by these testers discovered the sweeter kinds and those with right proportion of sweet and acid to be most agreeable. to the palate, use them for parents.

vors.

There is yet one point to consider, that is, that the vine as well as all other organic beings, transmits to its progeny somewhat of the impress of environment, hence the breeder of new varieties takes no pollen from sickly, starved, weakly or diseased plants, but only from the most robust and prolific in best quality fruit for the variety. This he secures by careful planting, cultivation, fertilization, pruning and training of the vines he uses as parents.

Thus it is the intelligent originator employs in combination all three means, cultivation, selection and combination of varietal and specific bloods to aid him in improving quality as well as other desirable features of the vine.

I have merely outlined the subject, which is sufficient suggestion to any but a novice. To treat the subject more specifically would be to open the entire subjects of cultivation and breeding of grapes, and clear out of range on this occasion.

I will close by mentioning some examples to illustrate some of the points of this paper.

Seeking a large, early fine quality red grape that would have perfect flowers, I cast about for parentage.

Delaware is too small, not heavy enough cropper, too dwarfish, too seedy and skinny and too subject to mildew in foliage, otherwise it is very fine, quality is best, skin thin and tough, not subject to black rot, persistent to pedicel, very handsome, Brighton was suggested as other parent, but it is so sensitive to black rot, that only by the most persistent spraying can the crop be saved. Then Lindley (Rogers No. 9) came to mind. It has a vigorous vine, it is very prolife when pollenized, has large clusters and large berries and a peculiar very agreeable flavor, the fruit resists black rot nearly as well as Delaware, its foliage resists mildew somewhat better than Delaware, I chose it for the mother, as it has reflexed stamens, and the Delaware for male parent, as it has erect stamens and abundent pollen. Of the various progeny, one came with large clusters, large berries, clear beautiful red of most delicious flavor and agreeable eating qualities, seeds few, pulp melting, skin a little too tender and so free from astringency that it can be eaten with pleasure, sweetness very high and acid in proper proportion to make it sprightly, not affected by black rot, very persistent to pedicel, sells the best of any grape in the local market, but too tender for long shipment. Vine vigorous and much longer lived than Concord in North Texas; but foliage mildews not so badly as Delaware but so as to weaken the vine if not sprayed. The flower is perfect and the vine very prolific, inclined to overbear, hence requires short arm pruning. It was named Brilliant. It succeeds where the Delaware does and is very popular where best known.

Again, wanting a variety entirely free from rots and mildews, of red color, of high quality, of late maturity adapted to the extreme south, among the various combinations, I used some Scuppernong blood (of the Southern Muscadine species, V. rotundifolia), as it has no diseases and grows to perfection anywhere in the South and ripens very late. It has bronzy white large berries, but unfortunately very small clusters and the berries drop as soon as fully ripe, two bad defects, and the skin is very thick and tough, seeds large, but flavor delicious and peculiar, greatly liked by all Southerners. The mother vine stood near some hybrids of Texas Post Oak grapes (V. lincecummii) which have large clusters, the berries persistent to pedicel, very vigorous and prolific, of excellent quality, very successful south. The Scuppernong standing alone cannot pollinate itself and as it blooms a little after the Post Oak grape when some of the belated flowers are still opening, I suppose some of the Scuppernong seeds were accidentally hybridized by the Post Oak hybrids. At any rate the Scuppernong bore some, although I did not myself pollenize the flowers, and I planted the Scuppernong seeds. Among the seedlings several showed some lobing of the leaves and bore much larger clusters than the Scuppernong, and the fruit had more sugar and they all were black, more persistent to cluster than the parent and far more

prolific and equally free from all diseases. The best two were named. and are being disseminated as LaSalle and San Jacinto.

The sacharometer shows the Scuppernong to have 63 to 65 sugar on Oeschle's scale and 5 to 5 per mill acid by Twitchell's acidometer, while the San Jacinto has 76 sugar and 5.8 acid, an ideal proportion and much richer than Scuppernong. The skin is much thinner than in Scuppernong and the seeds smaller, the flavor finer. It was this variety I chose, from which to breed my ideal late red southern improved Muscadine. I pollinized San Jacinto with Brilliant. In the lot of seedlings, several have a good red color, are still more persistent to cluster than San Jacinto, have quite thin skins, smaller seeds, are prolific to a fault, and perfectly free from mildew, rot and other diseases. One of these named Dixie is fine but berry not quite large enough; seems to be approaching to its grandparent Delaware in appearance of berry, yet considerably larger. Sugar 82; acid 8.4. Another named San Gabriel has a beautiful red good sized berry, thin skin, melting pulp, high quality, sugar 83, acid 7, seeds smaller than San Jacinto, cluster about the same size, some two to four times as large as Scuppernong. Another named Munson Muscat is as large in berry as Scuppernong, of a greenish white color, sugar 92, acid 7.5.

Thus in two generations I have raised the sugar content of Scuppernong 40 to 50 per cent, greatly thinned the skin, reduced the seeds, increased the clusters and productiveness, without getting any susceptibility to disease. But the flowers are yet imperfect, the clusters not large enough, the berries not persistent enough and the cuttings will not root readily enough, so that propagation must be by layers and hence slow.

There are other very interesting varieties in the lot. None of them have yet been offered for sale. I may introduce some of them. They are all very late. All endure cold better than Scuppernong, but are suitable only to a southern climate.

Such illustrations might be multiplied into many hundreds, each for some distinctive purpose, but sufficient have been given to suggest the method of procedure for any desired product.

LIGHT AS A FACTOR IN PLANT CULTURE: THE PROBLEM STATED AND ITS METHODS OF SOLUTION.

BY V. A. CLARK, Experiment Station, Tucson, Arizona.

The problem is to utilize or to apply light to the best advantage in plant culture in order to achieve predetermined ends. Light affects plants according to its intensity, that is quantitatively, and according to its composition that is qualitatively. Light also affects plants according to the form in which it strikes them, whether direct or diffuse; but this is, perhaps, really a special case under intensity. For when direct light strikes a plant the entire energy of the rays is concen

trated on those parts of the plant directly exposed to it; but if the light is diffused the same quantity is scattered over a larger surface and hence the intensity of impact is reduced.

Light of different intensities and of different compositions affects different parts of plants differently. Different anatomical structures, different molecular structures and different physiological processes are each affected in particular ways. In order intelligently to cause a plant to arrive at a particular and predefined development within the physical possibilities of its nature, in so far as said development is conditioned by light, the culturist must know how each representative structural or chemical component or physiological process of the plant is affected by light, what intensity of light and what selection of rays are necessary to the achievement of the purpose in hand, whether the promotion or the retarding of any plant process. When these conditions are known a rational plant culture with reference to light can be written and practiced.

The range of optimum light intensity for different parts of plants as for different species and varieties is great. For instance, the optimum intensity of light for root and stem growth is zero, while that for the formation of flowers and of sugar is the greatest compatible with the unchanged existence of chlorophyll. The research problem now becomes the purely physical one of light measurement. For this, one method is that of Roscoe-Bunsen as improved by Wiesner, which is based on the progressive darkening of a certain normal photographic paper according to length and intensity of exposure. This method would be very readily applicable in horticultural investigation. An objection to it is, that it is applicable only to the chemical end of the spectrum. There is need of developing a method for measuring also the intensity of light in the red end of the spectrum and of the total intensity of mixed light irrespective of its composition.

Another method which the writer has attempted is that of the Bunsen photometer, in which the two rays are brought together on an interposed screen of paper, stained with a grease spot. The differences between light intensities of the full sunlight and those of any common lamp or candle of known candle power as is commonly used in this method as a standard for comparison is so great that this method cannot be used without modification for measuring the intensity of the full sunlight. To obviate this difficulty, the writer has designed a photometer in which the sunlight is passed through a dispersing lens before striking the screen. The reduction in intensity is easily calculated by one of the simplest laws of optics.

By simple constructional adaptations an instrument is made, one end of which can be placed in the shade of a tree under a screen, while the end carrying the reducing lens lies outside of the shade exposed to the unobstructed sunlight.

Again when occasion arises for measuring light of very feeble intensity, similarly a condensing lens is used. The condensing lens will bring the light to an intensity directly and physically comparable with that of the lamp used as a standard of comparison. The method of the dispersing lens measures the intensity of the whole of a mixed

light, irrespective of its composition. Herein this method has an advantage over the chemical method in its present stage of development. But when only sunlight of different intensities is to be compared, probably the chemical method would doubtless give results sufficiently accurate for the purposes of horticultural investigation. The fact should be borne in mind, however, in using this method, that chemical rays are more absorbed by air and water vapor than the heat rays, and consequently this method would not give strictly comparable results as between humid and dry climates, low lands and mountain tops, and regions of different latitude, as, for instance, tropical and arctic regions.

As has been stated, light rays of different lengths have very different effects on the plant organism. In general, the less refrangible parts of the spectrum, the red rays, promote vegetative growth. A plant grown in red rays, which are physically most closely allied to the heat rays, partakes much of the nature of a plant grown entirely with the aid of heat and without light; but with this exception, that the red light somewhat inhibits stem growth and promotes leaf growth. The red rays are mechanical in effect and lead to exaggerated reduplication of the more primitive vegetative structure, but do not lead to increasing differentiation. The effect on the young plants is quantitative rather than qualitative. The highly refrangible rays, those at the blue end of the spectrum, are chemical and qualitative in their effect. They act upon the molecular structure producing transformations therein and thereby causing new developments within the plant substances. Hence they lead to increasing differentiation within the plant organism.

The form in which light strikes the plant is quite important, whether direct or diffuse. Strong direct light is relatively detrimental, hence cultural provision should be made for transforming direct sunlight into diffuse light. Natural provision for this is watery vapor in the atmosphere. One cultural expedient in an arid region would be slight shading.

The quantity of light which an individual should have is dependent to some extent on the degree to which various other environmental factors are operative. Light and heat are closely allied in their physical structure and they pass over readily into each other. To some extent, one can take the place of the other in plant culture. The lower the temperature, the greater must be the illumination, as in the case of arctic vegetation; and the higher the temperature, the lower may be the illumination as in the case of tropical shade flora.

Water and other forms of food supply are most economically used when light is at the optimum. The greater the divergence of light from this optimum, the more wasteful the expenditure of water and food. The statement of these relations should be expressed in numerical form.

Electricity is an environmental factor of some importance in plant culture. The question arises whether electricity could not to some extent take the place of light. Should this be found to be the case, a measured application of electricity would be a convenient cultural