Barnhart: Heteromorphism in Helianthemum 591 





Ed. 3> 36. 1897); and this, too, contrary to its original descrip- 

 tion, proves upon careful examination of authentic material to have 

 heteromorphous flowers. 



In certain respects the heteromorphism varies in different 

 species. In H. Canadense and H. majits the petal ifero us flowers 

 appear in spring, and are solitary, while the apetalous flowers are 

 autumnal and in clusters ; in the remaining species, however, the 

 petaliferous and apetalous flowers appear together, in the same clus- 

 ters and at about the same time. In H. Canadense, H. majus and 

 H. capitatum, the calyx of the complete flower is much larger 

 than that of the incomplete one ; in H. corytnbosum the contrast is 

 much less striking; while in H. Georgianum, H. arenicola and H. 

 Naskii there is practically no difference in the size of the calyx in 

 the two kinds of flowers. This probably accounts, at least in part, 

 for the fact that heteromorphism has never been suspected in the 

 last three species. The complete flowers are always on longer 

 pedicels than the incomplete ones, in some species many times 

 longer. Flowers intermediate in various degrees between those 

 with perfect expanding petals, and those with no petals whatever, 

 are occasionally present in some (perhaps all) of the species. 



Besides the features already noted, which may be seen at a 

 lance — the presence or absence of petals, the size of the calyx, 

 and the length of the pedicels — there are certain less conspicuous 

 but more important differences. In the complete flowers the sta- 

 mens are from 12 to 30 in number, and the filaments far exceed 

 in length the ovary and even the calyx ; the style is very short 

 but distinct, and the ovules are usually numerous (20-60, only 

 8-10 in H. capitation and H. Nashii). The incomplete flowers 

 are cleistogamous, and fertilized very early in the bud ; in them 

 the stamens are always less numerous than in the complete ones 

 (only 3-8), the filaments just enough shorter than the ovary, so 

 that the anthers are in contact with the stigma ; this rests upon 



g 



the summit of the ovary, but as it is large, and is contracted to a 

 small point of union with the ovary, it is more exact to say 

 "style obsolete" than "stigma sessile"; and the ovules are 

 always fewer than in the complete flowers of the same species, as 

 a rule less than half the number (6-20, only 3-6 in H. capitatum 

 and H. Nashii). Of course, the seeds are more numerous in the 



