188 SECTIONAL ADDRESSES. 



The Investigation of Freshwater Algae. 



The many new freshwater Algae that have become known in the present 

 century and that have contributed so largely to the foundation of the 

 concept of a parallel evolution in the different classes, show how much a 

 study of these forms may still be hoped to reveal. And at present the 

 field of research is restricted to quite a small area of the surface of the 

 globe. Over great parts of the earth the investigation of these forms is 

 only just commencing, and enormous tracts are still altogether unexplored 

 from this point of view, so that it is impossible to say what is yet to come 

 to light. Already in many families of Isokontae it would seem that almost 

 every conceivable variant of the central type has been evolved, and there 

 can be little doubt that the parallelism with which I have dealt in the 

 earlier part of this address will become still more striking, as investigation 

 proceeds and some of the present gaps become filled up. I propose there- 

 fore to devote the little remaining time to a few words upon the methods 

 of algal investigation. 



The position of England as the centre of a huge empire is responsible for 

 the fact that its few algal workers are inundated with demands for the 

 working out of collections made in its dominions and colonies. G. S. West 

 and his father devoted much time to such work which is very laborious, 

 and I have myself fallen a victim to it. It cannot, however, be suffi- 

 ciently emphasised that Algae are far better examined in the fresh condition, 

 for however well preserved, in these simple forms where details of cell- 

 structure are all important, much is obscured or becomes unintelligible. 

 It is greatly to be desired that competent botanists should take up fresh- 

 water algal investigation in different parts of the empire, and the activities 

 of a number of Indian workers in this direction is a matter for congratula- 

 tion. The necessary literature is now available in a fairly condensed 

 form, and willing assistance will always be furnished by those in this 

 country. 



Moreover, an Alga cannot be said to be properly known until it has 

 been studied at frequent intervals and, if widely distributed, examined 

 in its diverse habitats. In this respect almost everything still remains 

 to be done, even in our own parts of the world. Our cognisance of algal 

 genera and species is still very limited, because they have been mainly 

 studied on the basis of casual collections. True, in many cases (as for 

 example in Oedogoniales and Conjugatae) there are such decided repro- 

 ductive or vegetative characteristics that species can be broadly distin- 

 guished without a full knowledge of their complete range ; types with 

 the same essential characteristics at least recur frequently in different 

 habitats and in different parts of the world. But there are many groups 

 and genera, where no such decided characteristics exist, or where possibly 

 they still remain to be discovered, and where every algal worker has 

 again and again experienced the difficulty of a satisfactory determination ; 

 this is true, for example, of the majority of the Ulotrichales and Chaeto- 

 phorales, not to speak of the many difficult genera of Chlorococcales and 

 Myxophyceae. In all such cases we shall never arrive at a satisfactory 

 solution of the problem until a careful study has been made of the range 

 of variation of at least the commoner forms, not only in the course of 



