A. H. Trow 255 



several occasions during this study of groundsels, the difficulty of self- 

 sterility has been encountered. Exp. 48. In one case, that of a plant 

 isolated in the greenhouse (it was a monstrosity with fused cotyledons 

 and other malformations) which did not set a single seed, it was note- 

 worthy that all the flowers wei'e long-styled. Examples of long-styled 

 capitula are reproduced in PL XVII, figs. 16, 17 and 18. Long-styled 

 flowers have been frequently observed during the last three years, and 

 there is little doubt that the further study of them and their distribution 

 will help to clear away several difficulties. In another case, which 

 occurred in the F^ generation of lanuginosus x praecox, the plant was 

 a giant, the only one of the kind, and provided with very large ray 

 florets. Exp. 49. Yet not a single perfect seed was obtained from it, 

 although ultimately exposed to the pollination of all the other plants in 

 the garden. ' 



How are we to explain the results detailed in the table on page-254? 

 The 47 non-fimbriate plants of the Fi generation, as well as the parent 

 plant No. 17, were all clearly homozygous and FF plants. No. 6, one 

 of the parents ($) of the 49 plants of the Fi generation, was certainly 

 a,ff plant. If we suppose that the chance pollen grains which in this 

 case effected 'pollination were either / (22) or F (27), we get an ex- 

 planation of the mixed offspring. This provisional explanation is to 

 be tested in 1912 by isolating two_^' plants and obtaining seed from 

 them'. It is quite possible that the fimbriate character is such that 

 we shall always get under ordinary conditions nearly equal numbers 

 of_;y and FF individuals. We have to assume in this case that the ray 

 character depends not only upon the factor / but also upon the en- 

 vironment. The heredity would follow the same rule as prevails in 

 teazels with twisted stems, and in_ other " umschlagende Sippen." 



Hairiness. 



Hairiness is one of the most interesting and puzzling of the 

 characters which serve to define these elementary species of groundsel, 

 and has been investigated sufficiently to justify the publication and 

 discussion of some of the results. In the last edition of Koch's Synopsis, 

 1902, a single hairy variety is described under the name of sordidus, 

 with the brief description " Pfl. ganz spinnwebig-woUig." Rouy, in the 



' This was done, but the plants produced no ripe pollen. The 1912 examination leads 

 simply to the conclusion that all the fimbriate plants are female ? . It remains doubtful 

 whether it is possible to secure male fimbriate plants. 



18—2 



