November 13, 1914] 



SCIENCE 



709 



of folding in the bud, whereby one side is 

 deprived of light.) 



In the vinous series (red on primrose) we 

 have corresponding forms, one (var. vinosis- 

 simuSj nov.) having the rays entirely dark 

 wine red. 



On the whole, and in view of the fact that 

 there are no wild species of sunflowers with 

 red rays, it seems reasonably certain that the 

 red represents a " positive " variation ; but, as 

 with color variations in animals, there may 

 well be also a diluting or inhibiting factor, 

 which when present sensibly modifies the ex- 

 pression of the factor for red. It is not neces- 

 sary, however, to suppose even this, since vari- 

 ous degrees of stimulation might equally bring 

 about the results. Miss Wheldale, describing 

 analogous cases in chemical terms, suggests 

 that if the local oxidizing capacity of any 

 tissue is greater than its reducing power, this 

 is indicated by the local appearance of antho- 

 cyanin; if the reducing power is greater than 

 the oxidizing power, no pigment results. Thus, 

 she says, the loss of a dioxidizing factor would 

 produce color, as may be the case in the red- 

 leafed beech. 



Duggar found that in the tomato a red 

 pigment (lycopin) and a yellow (carotin) both 

 occur. In yellow varieties only the carotin 

 occurs; but in genetically red varieties a high 

 temperature precludes the formation of lycopin, 

 and yellow fruits result. In the case of the 

 red sunflowers, the red color very commonly 

 fades more or less after the flowers open, 

 probably in part owing to growth without 

 corresponding increase of pigment, which thus 

 becomes diluted. Dr. J. E. Schramm of the 

 Missouri Botanical Garden informs me that 

 in the hot summer of St. Louis this fading is 

 excessive, good red forms becoming practically 

 yellow before they are over. Also, on compar- 

 ing notes with Mr. D. M. Andrews of Boulder, 

 Dr. Schramm observed that roses with pale 

 tints are much less colored at St. Louis than 

 in Colorado. 



With regard to a possible " dilution " factor, 

 it is to be noted that in the series of yellow 

 and orange pigments, which occur in visible 

 particles, dilution can be seen, as explained in 



Science, August 21, 1914, p. 284. More re- 

 cently we have obtained the fourth possible 

 combination of this series, dilute orange, in 

 plants of the licolor-vinosus type. 



In the paper just quoted, irregularities in 

 the distribution of anthocyan pigments were 

 described. I have now to record a similar 

 peculiarity in which the solid pigments are 

 involved. An F, plant from very pale Heli- 

 anthus cucumerif alius X S. annuus coronatus 

 had broad orange rays, with about the basal 

 half strongly washed with chestnut. A single 

 ray, however, was primrose color, slightly 

 streaked with vinous. This ray had an orange 

 longitudinal stripe on the under side. The 

 difference here is only in the yellow, the differ- 

 ence in the red (chestnut and vinous) being 

 entirely due to the character of the background. 



A few words may be added regarding 

 gigantism. In 1913, and again in 1914, there 

 appeared among our red sunflowers a certain 

 number of gigantic plants, fully ten feet 

 high, nearly always with yellow rays. These 

 numbered perhaps about 25 per thousand 

 plants. The occurrence of these plants this 

 year has been especially striking, in a large 

 group of very good reds. One occurred, bloom- 

 ing very late, in the series of F, plants from 

 primulinus X coronatus, which gave us our 

 first vinous. Have we here a sort of jack-in- 

 the-box effect, some inhibitor of grov?th being 

 lacking in a certain number of cases? The 

 coronatus we used had some " Russian " (var. 

 macrocarpus D.C.) in its ancestry, which might 

 bring a recessive tendency to gigantism. 

 These large plants, however, were much 

 branched and had dark discs. 



T. D. A. CoCKEREIiL 



■University of Colorado 



x-ray diffraction patterns 

 The diffraction patterns discovered by 

 Friederich, Knipping and Laue have been 

 shown to be due to the arrangement of the 

 atoms of crystals into planes. These patterns 

 are used to indicate the spatial distribution 

 of atoms in crystals. 



An experiment illustrating these patterns can 

 be very easily shown to an audience by permit- 



