42 



DE. E. E. GATES— CONTEIBUTION TO A 



characteristic narrow, dark-green leaves often having red midribs. A young seedlin 

 is shown in PI. 5. fig. 57, and a nearly mature rosette in fig, 58. The young seedlings 

 are very characteristic, forming tiny, compact rosettes of dark-green leaves closely 

 hugging the ground. The number of leaves in the young seedlings seems to increase 

 much more rapidly than in O. biennis, O. grandifloray or O. La'nmrckiana forms, though 

 I have not determined the reason for this. The young plantlets also have a stouter, 

 harder (usually reddish) stem, and their roots are longer, making it more difficult to pull 

 them from the ground. All these differences are perhaps adaptations to a more rigorous 

 environment. Another collection of wild (naturalized) seeds from near Berlin, sent 

 through the kindness of Professor E. Eaur, yielded a uniform race apparently identical 

 with the last. In a culture of O. ammopJiila from the Bremen Botanical Garden 

 I was unable to find any constant distinction from certain races of 0. muricata. 



It is perhaps worth noting that in all cases where one uniform race was derived from 

 a collection, it was always a narrow-leaved type. Another interesting fact which shows 

 the extreme closeness between the organism and its environment, and the way in which 

 a slight environmental difference will induce a whole race of Oenothera to modify 

 markedly its development, is shown in my cultures, already mentioned, of O. muricata 

 var. canescens. In 1910 this race was grown in a very wet, rich soil, with much humus, 

 and the whole race (69 plants) without exception formed very imperfect rosettes and 

 then shot up slender, unbranched stems. The offspring from this race were grown the 

 following year in a much drier, poorer soil, without fertilizer, and with little humus. 

 These plants (22) again reacted uniformly in producing rather large rosettes, and, 

 finally, forming shoots with many long basal branches, giving them a pyramidal 

 appearance. The leaf and flower characters were, however, unchanged. Similar facts 

 are, of course, a matter of common knowledge to all who grow plants, but the numerous 

 and varied responses of which the plant is capable under varying environment are often 

 neglected or insufficiently considered, both in systematic descriptions and in experiments 

 on heredity. 



My studies of O. muricata from collections of seeds thus far renders it probable 

 that the individual races are less numerous and more wide-ranging than is the case 

 with O. biennis. It also seems probable that the O. muricata forms are, on the whole, 

 distinctly more northern in distribution than O. biennis^ there being possibly a relation 

 between smaller flower-size and higher latitude or altitude, though at present this is not 

 clear, for apparent exceptions occur. In any case, it could only be true in a very 

 general way. 



The following table summarizes my cultures of O. muricata races. Several other 

 cultures were unfortunately killed. The detailed description of these races will be 

 considered at another time. 



