116 HETEROSTYLED DIMORPHIC PLANTS. CHAP. III. 



and he was so kind as to send me specimens preserved in 

 spirits. The pistil of the long-styled form is nearly thrice 

 as long (i. e. as 14 to 5) as that of the short-styled, and is 

 very much thinner in the ratio of about 3 to 5. The folia- 

 ceous stigma is more expanded, and twice as large as that 

 of the short-styled form. In the latter the stamens are 

 about twice as long as those of the long-styled, and their 

 anthers are larger in the ratio of 100 to 70. The pollen- 

 grains, after having been long kept in spirits, were of the 

 same shape and size in both forms. The ovules, according 

 to Mr. Thwaites, are equally numerous (viz. from 70 to 

 80) in the two forms. 



VILLARSIA [SP.?] (GENTIANE.E). 



Fritz Miiller sent me from South Brazil dried flowers 

 of this aquatic plant, which is closely allied to Limnanthe- 

 mum. In the long-styled form the stigma stands some way 

 above the anthers, and the whole pistil, together with 

 the ovary, is in length to that of the short-styled form as 

 about 3 to 2. In the latter form the anthers stand above 

 the stigma, and the style is very short and thick; but the 

 pistil varies a good deal in length, the stigma being either 

 on a level with the tips of the sepals or considerably be- 

 neath them. The foliaceous stigma in the long-styled form 

 is larger, with the expansions running farther down the 

 style, than in the other form. One of the most remarkable 

 differences between the two forms is that the anthers of 

 the longer stamens in the short-styled flowers are con- 

 spicuously longer than those of the shorter stamens in the 

 long-styled flowers. In the former the sub-triangular pol- 

 len-grains are larger; the ratio between their breadth 

 (measured from one angle to the middle of the opposite 

 side) and that of the grains from the long-styled flowers be- 

 ing about 100 to 75. Fritz Miiller also informs me that the 

 pollen of the short-styled flowers has a bluish tint, whilst 

 that of the long-styled is yellow. When we treat of Lyth- 

 rum salicaria we shall find a strongly marked contrast in 

 the colour of the pollen in two of the forms. 



The three genera, Menyanthes, Limnanthemum, and 

 Villarsia, now described, constitute a well-marked sub- 

 tribe of the Gentianea3. All the species, as far as at pres- 



