Varietäten, Descendenz, Hybriden. 147 



pus, one occurring in Vera Cruz and the other on the opposite 

 side of the continent in Low er California. 



In Rubus villosiis and R. strigosus, both very variable species, 

 the pollen is extremely bad. Where these species occur on islands, 

 hovvever, the pollen is generally much more perfect, probably as 

 the rcsult of Isolation. R. deliciosiis, a species of limited geographic 

 ränge, has pollen practically entirely perfect. Also in the species 

 R. odoratus, which blossoms after the mass of other species have 

 shed their flowers. 



Variabilit}'^ and gametic sterility coincide in Betula, Qiierciis, 

 Solanuju , Alopeciirus, Potatnogeton and manj'^ others; monotypic 

 species and perfect pollendevelopment are found together in Z/^rtw/a 

 aquatica, Zannichellia, Zostera, a. o. Similar Statements hold in a 

 like sense in regard to members of the Alismaceae, Spargania- 

 ceae etc. 



The general condition in the Angiosperms in contrast to the 

 Gymnosperms is a large degree of variability in the species. Where 

 interspecific crossing is possible, there is often clear evidence of 

 its presence in the form of a high degree of variability, accompa- 

 nying a considerable manifestation of sterility in the pollen. 



If associated variability and gametic sterility are reliable indi- 

 cations of hybridization, then it becomes clear thatthe Angiosperms, 

 unlike the Gymnosperms and the mass of the vascular Cryptogams, 

 are often characterized by heterozygosis. There is great evidence 

 for assuming hybridization as having an incalculably large effect 

 on the rate of evolution in Angiosperms, but not so in Gym- 

 nosperms and vascular Cryptogams. Universal hybridism as the 

 sole cause of Variation put forward by Lotsy, is rejected as much 

 too sweeping. The small variations of homozygous Stocks as in 

 Gymnosperms clearly prevailed in the earlier history of our earth, 

 while the niore rapid changes which have ensued in later times 

 are correlated, so far as plants are concerned, at any rate, with 

 marked physiographic and climatic differentiation, and most impor- 

 tant of all with the phenomenon of hybrization. 



M. J. Sirks (Bunnik). 



Leigthy, C. E., Carman's wheat-rye hybrid. (Journ. of He- 

 redity. VII. p. 420—427. 1916.) 



The paper teils us the history of the nine different hybrids, 

 made about 1890 by E. S. Carman, who thought them all to be 

 hybrids between wheat and rye; but the writer declares that eight 

 of them, in which no trace of the rye could be detected, nor in 

 their progeny, must have actually resulted from fertilizations of 

 wheat flowers with wheat pollen. But one, a nearly sterile plant 

 that most resembled rye, was neither wheat nor rye, but had the 

 modified characters of each. The shape and general appearance of 

 the head, the arrangement and number of spikelets, and the glume 

 characters were all such as are commonly found in wheat-rye hy- 

 brids. The culm resembled that of rye, except in color, having the 

 whitish down near the head which never appears in wheat. This 

 plant bore ten heads which produced but nineteen kerneis, thus 

 being nearly sterile. All of these characters combined allow no 

 question of this plant being actualy a hybrid between wheat and 

 rye. One of the varieties, derived from Carman's crosses, k?nown 

 as Rural New Yorker no 6, seems to be actually descended from 



