120 



SCIENCE 



[X. S. Vol. XXXII. No. 812 



becoming manifest when conditions favoring 

 transpiration are marked." The disease is 

 therefore not due to the presence of parasitic 

 organisms, but is what has been rather 

 loosely called a physiological disorder. 



In a short paper in the Annales du Jardin 

 Boianique de Buitenzorg (2d Ser., Supp. III.) 

 Professor Eamaley enumerates and discusses 

 the European plants growing without culti- 

 vation in Colorado. In addition to an an- 

 notated list of species the author discusses the 

 region included, and the mode of introduction 

 and occurrence of the species. Botanists who 

 have not given attention to these immigrants 

 will be much surprised at the extent of the 

 list. 



Professor Sargent continues his studies 

 of the species of hawthorns in Pennsylvania 

 in a paper entitled " Crataegus in Pennsyl- 

 vania, II.," published in the Proceedings of 

 the Academy of Natural Sciences of Phila- 

 delphia (March, 1910). His first paper on the 

 Pennsylvania hawthorns appeared about five 

 years ago, since when much additional mater- 

 ial has become available for study, resulting 

 in a thick pamphlet of about one hundred 

 pages. In this space the author enumerates 

 and describes 110 species, of which SO are de- 

 scribed as new! Think of what the new edi- 

 tions of the botanical manuals will have to 

 contain when these new species are added! 

 We may have to grant the necessity of dis- 

 tinguishing these forms from one another in 

 descriptive botany, but what an amount of 

 work will have to be done by the taxonomists 

 of the future in reducing these multitudinous 

 forms to such categories as wiU be distin- 

 guishable by botanists, other than specialists 

 in the hawthorns ! 



Charles E. Besset 



The Ukiveesity of Xebraska 



SPECIAL ARTICLES 

 ~j SEX LIMITED INHERITANCE IN DROSOPHILA 



In a pedigree culture of Drosophila which 

 had been running for nearly a year through a 

 considerable number of generations, a male 

 appeared with white eyes. The normal flies 

 have brilliant red eyes. 



The white-eyed male, bred to his red-eyed 

 sisters, produced 1,237 red-eyed offspring, 

 (Fj), and 3 white-eyed males. The occur- 

 rence of these three white-eyed males (P^) 

 (due evidently to further sporting) will, in 

 the present communication, be ignored. 

 The F^ hybrids, inbred, produced: 

 2,459 red-eyed females, 

 1,011 red-eyed males, 

 782 white-eyed males. 



No white-eyed females appeared. The new 

 character showed itself therefore to be sex 

 limited in the sense that it was transmitted 

 only to the grandsons. But that the character 

 is not incompatible with femaleness is shown 

 by the following experiment. 



The white-eyed male (mutant) was later 

 crossed with some of his daughters (F^), and 

 produced : 



129 red-eyed females, 

 132 red-eyed males, 

 88 white-eyed females, 

 86 white-eyed males. 



The results show that the new character, 

 white eyes, can be carried over to the females 

 by a suitable cross, and is in consequence in 

 this sense not limited to one sex. It will be 

 noted that the four classes of individuals 

 occur in approximately equal numbers (25 

 per cent.). 



An Hypothesis to Account for the Besults. 

 — The results just described can be accounted 

 for by the following hypothesis. Assume that 

 all of the spermatozoa of the white-eyed male 

 carry the " factor " for white eyes " W " ; that 

 half of the spermatozoa carry a sex factor 

 " X " the other half lack it, i. e., the male is 

 heterozygous for sex. Thus the symbol for 

 the male is " VV VVX," and for his two kinds 

 of spermatozoa WX — W. 



Assume that all of the eggs of the red-eyed 

 female carry the red-eyed " factor " E ; and 

 that all of the eggs (after reduction) carry 

 one X, each, the symbol for the red-eyed 

 female will be therefore EEXX and that for 

 her eggs will be EX — EX. 



When the white-eyed male (sport) is crossed 

 with his red-eyed sisters, the following com- 

 binations result: 



