THE CEYLON SPECIPJS OF CAULERPA. 101 



depend exclusively on clianges in the purely vegetative sphere, for no organs of fructification nor 

 spores of any kind are to be found in these plants, and Reinke has, therefore, hit the mark when he says 

 tftat the somatic plasma is the medium in and through which the variations at the Gaulerpas originate. 



IV.— TAXONOMY OF THE CAULERPAS.— DEFINITION OF THE SPECIES. 



It is clear that, as long as we have no firm basis for determining the factors which cause the 

 formation of a species, we can have no real objective principles by which we can determine its 

 limitations. It is for this reason that the conception of the specific character of a species 

 varies more than anything else in the different works on Caulerpas. While some authors prefer 

 small but often less sharply distinguishable species, others prefer wider species, under which are classi- 

 fied a huge number of sub-species, varieties, and forms, often without it being possible for the reader 

 to explain why a certain form should be called there "variety," now only "form." 



In this respect also the Caulerpas have been subjected to various fates. Lamouroux, the 

 founder of the genus Caulerpa, knew 10 species in 1809. Since then new species have been described, 

 one by one, and Kutzing could enumerate 41 species in 1849, divided by him into several genera. The 

 first really valuable monograph on the genus Caulerpa was published by J. G. Agardh in 1872, and he 

 could then distinguish no less than 64 species divided into 13 groups. In 1898 Madame Weber v. Bosse, 

 in her monograph, reduced the number of the species to 54, but these species have numcous sub-species 

 and varieties of different rank. It is undoubtedly a great merit in her work that thereby the unity, 

 the great affinity between the various forms, is so strongly accentuated. But, as Reinke so felicitously 

 points out, it is not necessary to group together different species even if transition forms can be found 

 between them. For besides the practical difficulties that accompany such a taxonomy — for one is forced 

 to use as many as four different names (species, sub-species, variety, form) to make quite clear what 

 one is refering to — so too from a purely theoretical point of view one must note that one might just as 

 well reduce the whole genus to one, or a few species, dependent on whether one assumes a monophyletic 

 or polyphyletic origin. But systematic botany ought to lay stress not only upon unity but also upon 

 diversity, and from this point of view it seems more satisfactory to me to employ a more limited species 

 definition, as the older authors did. The genetic relationship of the different species is then not confused, 

 at any rate. 



If we apply this to the Ceylon species of Caulerpa it is really only the group clavifera-uvifera-lcete- 

 virens-Chemnitzia-peltata that makes difficulties ; for in this group the diversity is greatest. While some 

 Ca«?erpa-species, as verticillata, crassifolia, sertularioides , are less variable, the race.mosa group (Weber 

 V. Bosse) on the other hand, as observed above, is especially rich in forms. It is evident that the genus 

 Caulerpa, as so many otlier genera of plants, shows types of different constancy. While some species 

 vary but Uttle, in other groups the variety is very great and probably new forms are now originating. 

 It is thus probable that in Ceylon this is the case with forms belonging to clavifera, uvifera, Chemnitzia, 

 peJiata, nummularia^ and others. In this connection it must be observed that geographical distribution 

 in some cases quite clearly shows that the different groups of forms have in part a tendency to have 

 a distribution which excludes other groups ; so, for instance, C. Chemnitzia, uvifera, and their forms occur 

 especially in the north of Ceylon, whereas C. clavifera and nummularia, have more predominantly 

 southern distribution. This may possibly be bound up with the conditions of life being so different in 

 different parts of the Island, coral-reefs and rocks in the south, sand in the north. 



But with respect to the geographical distribution of these algae in Ceylon and its causes, this 

 problem, until I have had an opportunity of studying all the algae of the island, can only be dealt with 

 by me cursorily 



