HETEROSTTLISM. 217 



Oa tbe other hand, the anthers of the short-styled are 

 usually longer and contain larger pollen grains than those 

 of the long-styled, the pollen of which is also often more 

 translucent and smoothei-. 



Of all the species included in the above-mentioned thirty- 

 six species, only five seem to have the pollen of both forms 

 of the same size, and two in which it was reversed. The 

 five species are Leucosmia Burnettiana, Linum grandiflorum, 

 Cordia, Gilia pulchella, and Coccocypselum. The two in which 

 the pollen grains of the long-styled form were the larger, 

 were Gilia micrantha and Phlox subulata. 



The presence of cases where the usual differences are not 

 pronounced is just what one expects to find, in accordance 

 with the laws of differentiation ; whereby intermediate 

 conditions are to be looked for. Thus some species of 

 Primula afford great differences in the shapes of the stigmas, 

 P. veris being globular in the long-styled, and depressed 

 in the short-styled; while in P. Sinensis it is elongated: 

 but in other species, as P. Sikkimensis and P. farinosa, there 

 is but little difference between the stigmas of the two forms. 

 In some cases the differences reside entirely in the stamens or 

 pollen grains, as in Forsythia suspensa, in which, although 

 (contrary to the rule) the anthers of the long-styled are in 

 length as 100 : 87 compared with the short-styled, yet the 

 pollen grains are as 94 : 100, which agrees with the rule. 

 'Wiih Linum grandiflorum and Cordia and Gilia pulchella, etc., 

 the difference lies in the pistil. On the other hand, the 

 difference may reside in the stamens, as in ^giphila elata, 

 the pollen grains being as 62 : 100, i.e. in the long-styled as 

 compared with the short-styled. 



^giphila obdurata has the stigmas of the long-styled 

 in length 100 : 55 as compared with the short- styled ; and 

 the length of the anthers as 44 : 100. This is, therefore, 



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