156 CALLITRIOHE TRUNCATA. 



tration he gives a new plate (t. 1273) of C. hamulata, Kiitz., though 

 expressing a strong opinion tliat C. peduuculata and C. hamulata are 

 but varieties of one subspecies. 



The character which at once separates C. truncata from C. pediin- 

 culata, and from all Callitriches except G. autiimnalis, is to be found 

 in the structure of the fruit. In most species the lateral or marginal 

 furrows between the adjacent carpels are shallow, never reaching to as 

 far as halfway to the axis of the fruit; but in C. anlumnaUs and C. 

 truncata the furrows are very deep, almost meeting, and so constricting 

 the fruit into halves. 



The accompanying diagrams represent transverse 

 sections of the fruit of (1) C. autamnaUs, from An- 

 glesey ; (2) C. truncata, from Sussex, and (3) C. pe- 

 dunculata, from Cumberland, all enlarged about ten 

 diameters. It is, however, but rarely that all the 

 component carpels are equally developed. 

 From C. pedmiciilata and C. hamulata, our plant also 



, „ . ,. differs in being always entirely submerged, in being 



1. C. autumnal IS. . ° " . ■ , . , . 



2. C.trnnoata. destitute of the peculiar stellate scales, m having 



3. C.pedunculata. leaves of a deep, clear, pellucid green, and all similar 

 in form, none being ever spathulate, and in the entire want at all times 

 of floral bracts. The submerged leaves of C. pedanculata and G. hamu- 

 lata are usually also much longer in proportion to their breadth than in 

 C. truncata. In all these points the latter approaches C. autumnalis, 

 from which it is distinguished by the carpels not being winged, by the 

 fruit being smaller, and the whole plant more slender and delicate, and 

 by the earlier date of flowering. I can see no ditference in the leaves 

 beyond the distinction in size and greenness; the leaves of C. autum- 

 nalis are not always wider at the base. 



Mr. Borrer, with his usual acuteness, noticed several of these points, 

 e.g. the want of bracts, and the invariably submerged habit. Mr. 

 J. de C. Sowerby also, who cultivated the plant for two years, was 

 particularly struck with the perfectly achlamydeous character of its 

 flowers, and with the fact, that " the leaves never spread upon, or 

 even reach the surface of the water, whatever its depth may be ; " he 

 also described rightly the fruit as wingless, and observed that two or 

 three seeds were often abortive (see his MS. notes on the original 

 drawing for E. B. Supp. 2606, in the British Museum). It is worth 



