4 CHLOROSPERME^. 



unicellular Algte of Braun are the lUiile organs or androspores of other Algoe. I think 

 it can hardly be questioned that multitudes of the Palmelloid forms are either spores or 

 imperfectly developed fronds ; and the same is probable of many Confervoids. As yet 

 the subject, except in a few able hands, has been confused rather than rendered more 

 clear by the labour bestowed by authors upon it. There has been too great an anxiety 

 to establish new genera and species, without due regard being had to circumstances of 

 gi-owth and development ; and the unfortunate student who now attempts to study 

 tlie fresh water Algte is oppressed by an accumulating mass of bad species and genera, 

 which all have to be in some degree mastered before he can make clean worlc. Adcf 

 to this, that in the present state of our knowledge it is absolutely necessary, in most 

 instances, to have the living plant at hand, and it will be understood what a difficult 

 task it must be to give a good account of the Chlorospermatous series of the Algae. 



No one can be more sensible than I am myself of the very imperfect nature of the 

 sketch attempted in the present memoir. I write at a distance from my subject, and 

 have rarely had more than dried specimens to examine. Though many of them Avere 

 personally collected by myself in 1850, when travelling in America, o;:i very few have I 

 preserved notes taken from the recent plant. This is jjerhaps of less account among 

 the marine kinds, which formed the staple of my personal collections, for the marine 

 species reco\er their cliaracters on re-immersion much more perfectly than the fresh 

 water kinds. But the want of living specimens has seriously barred my attempts to 

 describe tlie fresh water species, with the exception of such easily preserved kinds as 

 Hi/drodicti/on, Batrachospermum, Lemanea, Petalo7iema, &c. The Zygnemaceaj, of 

 which I have received several, and which are probably numerous in America, so com- 

 pletely lose their distinctive characters in drying, that I have been forced to omit them 

 altogether. So also it has happened with the species of Oscillatorla^ and of the Con- 

 fer\'oid Algte generally. I must therefore leave the task of describing the fresh water 

 Algte of America to other hands ; to some one living among them, and having eyes 

 fully open to the difiiculties of his task, and zeal and ability to work it faithfully. And 

 here I cannot omit a slight tribute to the memory of one in whom were combined in 

 no common degree the qualifications which make an able naturalist, and who, had lie 

 lived, would probably have taken up the broken thread. 



I allude to the late Professor J. W. Bailey of Westpoint, one of the earliest explorers 

 of American Algaj, and whose very able memoirs on the Diatoniacew have won for him 

 an imj)erishable name in the annals of science. To me his loss is more personal than 

 to most of his botanical friends, for from the hour we first met there grew up between 

 us a warm friendship which death has interrupted, but which I trust it has not ended. 

 He it was who first suggested to me a Memoir on the American Alga3 ; he arranged 

 with the Smithsonian Institute the terms of its publication ; he supplied me with a 

 multitude of specimens ; and to his influence I owe the assistance 1 have received from 

 many American algologists who looked up to him for direction in their studies. He 

 was, as far as the Alga; are concerned, my chief American referee, to whom I could 

 apply when seeking information on local matters, connected with this branch of study. 

 AVith him I constantly associated my work, and to his approbation I looked forward as 



