THE CEYLON SPECIES OF CAULERPA. Vi:i 



in my opinion, to have really hit upon the true character of this type. For, if we examine Harvey ',s 

 type-specimen (Friendly Isl. Alg. No. 77, at least the examples which are preserved in the Herbarium 

 in the R. Riksmuseum in Stockholm) we shall find that, in reality, there are very few discs which are 

 crenulate, and not in a single case have I been able to verify that a new stalk grows out from the crenule 

 of the disc. Every time I thought I had found such a case the stalk in reality shot out from the stalk 

 of another disc ; but owing to the pressing it had had, this was not evident, and it seemed to emanate 

 from the crenule itself. On the other hand, it is very characteristic that the side-branches which support 



Fig. 35. — C. nummulariu {B.A.nv.) REii^KK. (3 x 1). 

 the assimilation discs become procumbent and take root ; and the result is naturally a mode of branching as 

 Reinke described it, i.e. , the assimilation discs grow directly out from the rhizomes. Fig. 35 shows a picture 

 cf C. nummularia from the side. From the elongated creeping rhizome emanate numerous side branches 

 and also single branchlets. The former become procumbent and form rows of horizontally placed assimi- 

 lation discs. The branch formation may be so plentiful and the assimilation discs so numerous and 

 close that such a tuft, seen from above, only shows the shape of a mass of assimilation discs without 



Fig. 36. — C. nummularia (habv.) reinke. (1 x 1). 



apparent order, crowded about each other (fig. 36). This results from nummularia, in the same way 

 as C. davifera, being a pronounced hght alga, and so belonging to the uppermost parts of the littoral zone 

 just as in davifera its whole assimilation system is horizontally broadened out in one level. Hence the 

 tuft formation is distinctly carpet-hke. 



Undoubtedly this form is derived, as perhaps an ecological race, irompeltata (main form), and the 

 transition forms which I have already described show this very evidently ; the horizontal axes in the 

 form from Kangesanturai (fig. 32) have precisely the mode of branching characteristic of nummularia. 

 To what extent light directly afl^ects the formation of these forms, I do not venture to decide. But 

 to judge from the difference between the intense light in the upper littoral zone, where C. davifera and 

 C. nummularia occur, and which, at low water especially, when they are nearly uncovered, is naturally 

 of great strength compared with the shading that takes place in the deeper localities where C. uvifera 

 and C. peltata occur, one is tempted to presume that this mode of growth depends to a certain extent 

 on the light. Experiments alone can decide tliis point satisfactorily. 



