88 PKYLOX MARINE BIOLOGICAL KKPORTS. 



If we examine the assimilation system in the Ceylon Cuulerpas, we shall find sev-eral different types 

 and variations. They may be roughly divided into two groups, viz., such as have the assimilation 

 system very strongly branched (always a system of short shoots, pinnules), and such as in their assimila- 

 tion organs have a measure of correspondence witli. or at least some outward resemblance to, the leaves of 

 the higher plants. To the latter group belong such forms as C. scalpellijormis (fig. 2), crassifolia, taxifolia 

 (figs. 4, 5). &c. ; to the former such as verticillata (fig. 1). clavifera (fig. 13), uvifera (fig. 15) , loetevir ens (^g. 

 19), &c. But a division of this kind is of course incomplete and vague. For it could also be expressed in 

 this way : the one group (the leafy one) is characterized by its assimilation branches being bilateral, the 

 other by its axes being radial. But here it is to be observed tliat only the main axes are radial, the lateral 

 axes or the short shoots may afterwards assume the most variable shapes. They, too, can be radial, i. e., 

 cylindrical as in C. Icetervirens /. laxa, cylindi'ical with spherical point as in C. loncistipitata (fig. 45), 

 crassicaulis {fig. 47), clavifera, uvifera, d:c.: finally, disciformly flattened, as in C. w^iwm%tor^a (figs. 35,36). 

 imbricata (fig. 30), and others. The questions now arise whether in these various leaf and shoot forms we 

 can see any adaptations to their different surroundings ; whether one can be considered in any way more 

 perfect than another, or whether they are all equally good for the purpose, and whether really the great 

 variability is only to be ascribed to formative energy in the plant that escapes our direct observation. 

 We will deal with these in that order. 



(A). — The bilateral leaf-like Caulerpas. 



It seems to me indisputable that the leaf -like flat Caulerpas are derived from radial forms as being 

 the more primitive ones ; that they are very closely related is shown already by such a species as G. flagelli- 

 formis, of which there are both radial and flattened forms, very similar to one another and often passing 

 over from the one to the other. Such a fine leaf -like species as C. prolifera can even be transformed, as 

 Klemm has shown, into the cylindrical form, exactly in the same manner as several species of Opuntia. 



A comparative examination of the assimilation axis of th(^ trilateral species shows moreover that 

 the bilateral axes are often radial at the base, and there form branch lets round the axis. This by no means 

 lare case is illustrated in this work by C. Lessonii (fig. 11, the branches to the left of the picture), by 

 C. taxifolia f. tristichophylla (fig. 5) , and also by C. dichotoma (fig. 24. a) where some branches at the base 

 show weak indications of radial arrangement. It is evident tiiat by the lateral arrangement a surface 

 increase has been gained, the advantage of which for the work of assimilation is self-evident. So far, as 

 great an increase of .surface as possible were desirable, provided no disadvantage were involved. But 

 such is undoubtedly present; the large flattened leaf -like organ, without any special mechanical 

 elements or tissues, runs a great dangei' of splitting if exposed to too violent a strain, in the form of 

 ground-swell or the like. That Caulerpa prolifera is actually very susceptible to tliis, and cannot 

 withstand a too turbulent sea follows very clearly from .J.vnse's notes ("Bewegun. d. Protoplasma von 

 Caulerpa prolifera , " p. 166) on broken Caulerpas in the Gulf of Naples after very stormy weather, which has 

 stirred up even the quiet depths where C. prolifera lives. It is evident, therefore, that if such broad- 

 leafed forms are to have any chance of living it must be in sheltered places, and, of course, especially at 

 considerable depths that are not disturbed by heavy seas. In this respect l\ow does the matter stand 

 with the other leaf-like Cauleri)as ? It has already been pointed out above tliat C. prolifera is by pre- 

 ference a deep water form, both in the Mediterranean and in the West Indies, The same may be asserted 

 of C.scalpelliformis. In the littoral zone I only found it once, at Paumben, and for the rest it is wanting 

 in the httoral zone of Ceylon. As, however, it has been noted from the pearl banks in the Gulf of Mannar 

 (E.S.Barton, "Listof Marine Alga^ collected . . . .at Ceylon," p. 165), and has moreover been obtained by 

 .lOHs. Scii.vnoT at as great a depth as 15 metres and more in the Gulf of Siam ("Koh Cluing," IV., p. 104), 

 and as it is mentioned by Harvey ("Phycologia Australica, " I., PI. 17) as growing "a few feet below the 

 low- water mark," we may consider ourselves justified in not counting C. .smZ/W/jYormts among the typical 

 algae belonging to tlie uppei littoral zone, but as a (/aulorpa which prefers .somewhat deeper regions. 



