124 HETEEOSTYLED DIMORPHIC PLANTS. Chap. III. 



about the ratio of 100 to 62. The two forms of ^. mollis 

 present a like difference in the length of their pistils and 

 stamens. 



MsmBILA. OBDURATA. 



Flowers of this bush were sent me from St. Catharina in 

 Brazil, by !Fritz Miiller, and were named for me at Kew. They 

 appeared at first sight grandly heterostyled, as the stigma of 

 the long-styled form projects far out of the coroUa, whilst the 

 anthers are seated halfway down within the tube; whereas in the 

 short-styled form the anthers project from the coroUa and the 

 stigma is enclosed in the tube at nearly the same level with the 

 anthers of the other form. The pistil of the long-styled is to 

 that of the short-styled as 100 to 60 in length, and the stigmas, 

 taken by themselves, as 100 to 55. Nevertheless, this plant 

 cannot be -heterostyled. The anthers in the long-styled form 

 are brown, tough, and fleshy, and less than half the length 

 of those in the short-styled form, strictly as 44 to 100 ; and 

 what is much more important, they were in a rudimentary 

 condition in the two flowers examined by me, and did not 

 contain a single grain of pollen. In the short-styled form, the 

 divided stigma, which as we have seen is much shortened, 

 is thicker and more fleshy than the stigma of the long- 

 styled, and is covered with small irregular projections, formed 

 of rather large cells. It had the appearance of having suf- 

 fered from hypertrophy, and is probably incapable of fertiti- 

 sation. If this be so the plant is dioecious, and judging from 

 the two species previously described, it probably was once 

 heterostyled, and has since been rendered dicecious by the 

 pistil in the one form, and the stamens in the other having 

 become functionlfess and reduced in size. It is, however, 

 possible that the flowers may be in the same state as those of 

 the common thyme and of several other Labiatse, in which 

 females and hermaphrodites regularly co-exist. Fritz Miiller, 

 who thought that the present plant was heterostyled, as I 

 did at first, informs me that he found bushes in several places 

 growing quite isolated, and that these were completely sterile ; 

 whilst two plants growing close together were covered with 

 fruit. This fact agrees better with the belief that the species is 

 dioecious than that it consists of hermaphi-odites and feifiales ; 

 for if any one of the isolated plants had been an hermaphrodite, 

 it would probably have produced some fruit. 



