116 HETEROSTYLED DIMOEPHIC PLANTS. Chap. HI. 



LiMNANTHEMUM InDIOUM (GeNTIANE^). 



This plant is mentioned by Mr. Thwaites in his Eniuneration 

 of the Plants of Ceylon as presenting two forms; 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 foliaceous 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 poUen-grauis, after having been long kept in spirits, were 

 of the same shape and size in both forms. The ovules, accord- 

 ing to Mr. Thwaites, are equally numerous (viz. from 70 to 80) 

 in the two forms. 



VlIiLAESIA [SP. ?] (GeNTIANE*). 



Fritz Miiller sent me from South Brazil dried flowers of this 

 aquatic plant, which is closely aUied to Limnanthemum. 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 antters 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 beneath them. The foliaceous stigma in 

 the long-styled form is larger, with the expansions running 

 farther down the style, than ia 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 conspicu- 

 ously longer than those of the shorter stamens in the long-styled 

 flowers. In the former the sub-triangular pollen-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 being about 100 to 75, Fritz 

 MiiUer also informs me that the poUen of the short-styled 

 flowers has a bluish tint, whilst that of the long-styled is yellow. 

 When we treat of Lythrum 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 Gen- 

 tianesB. All the species, as far as at present known, are hetero- 

 styled, and all inhabit aquatic or sub-aquatic stations. 



