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BOTANICAL GAZETTE [january 



requirements. The experiments to be described in this article are . 

 limited to the effects of their pollen on 0. lata and O. scintillans. 

 O. strigosa Rydb. has very small flowers, of the size of those of 

 . O. muricata, but in less dense spikes. They open their anthers 

 two or more days before unfolding the corolla, and the pollen comes 

 in contact with the whole outer surface of the stigma and causes 

 fertilization. The leaves are bluish green and furrow-shaped, and 

 the tip is bent sideways. The tops of young shoots, when seen from 

 above, therefore, present the aspect of a wheel with spokes all curved 

 to the left or to the right. This striking feature is repeated, though 

 somewhat reduced, in all of its hybrids and causes them to be easily 

 recognized. I collected seed in the Yellowstone Park in 1904. 

 Another lot was kindly sent to me by Mr. T. D. A. Cockerell from 

 Boulder, Colorado. Of both strains I have since cultivated two 

 generations. 



In crossing O. strigosa with O. Lamarckiana, twins arise which 

 combine the characters of laeta and velutina with those of strigosa. 

 They differ more widely from one another than do the twins of any 

 other cross I have studied up to this time. The velutina is almost like 

 the velutina of O. muricata X Lamarckiana, but has the bluish tinge, 

 the more pointed leaves with bent tips, and the wheel-shaped tops 

 of the young shoots described above for O. strigosa. The laeta from 

 the strigosa cross is a very stout plant with very broad leaves (6 cm ), 

 blunt at the apex and indented at the base, with smooth surface, and 

 bright green. The flower buds are more narrowly conical than those 

 of velutina, the flowers open more widely, the fruits are conical with 

 four sharp and protruding teeth, whereas those of velutina are blunt 

 and short. By this mark and by the somewhat narrowed neck of the 

 fruits of velutina, the two forms are most easily distinguished when 

 flowering is over. The laeta is usually poor, but the velutina is rich 

 in pollen. 



In contrast to the species previously dealt with, O. strigosa pro- 

 duces twins from O. Lamarckiana when used as male parent as well 

 as when used as female parent. In these reciprocal crosses both of 

 the twins are identical. 



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The twins produced by O. strigosa from O. scintillans and from 

 O. lata comply with the description given. They cannot be distin- 



