Introduction 3 



Exception may be taken to the rejection of Cohn's group of 

 the Schizophyta, which was instituted to include the Schizomycetes 

 (or Bacteria) and the Schizophyceae (or Blue-green Algae). These 

 two series of plants undoubtedly present a similarity in their 

 method of multiplication by simple cell-fission, but it must be 

 remembered that most unicellular and colonial Algae habitually 

 multiply in this manner, and although the Bacteria stand near in 

 this respect to some of the less differentiated Blue-green Algae, 

 there are many reasons for not including the two series of organisms 

 in the same group. The Blue-green Algae possess chlorophyll and 

 phycocyanin disposed within the cells in the manner of a primitive 

 chromatophore, and are thus capable of carbon-assimilation ; whereas 

 in the Bacteria this is not the case. A ciliated motile condition 

 is only known to occur in about two blue-green organisms, whereas 

 that is the normal condition in most of the Bacteria ; and the 

 spore-formation, with very few exceptions, is quite different in the 

 two groups. The Myxophyceae are also of a much higher type of 

 organization than the Bacteria, possessing a primitive nucleus 

 (which in the Glaucocystidjk has become a true cell-nucleus) and a 

 cell- wall composed partly (and in the case of certain cells, entirely) 

 of cellulose. Moreover, the habits and mode of life of most of them 

 are totally different from those exhibited by the Bacteria. 



In this volume the Blue-green Algae are placed in the class 

 Myxophyceae (Stizenberger, I860) 1 , which is an earlier name than 

 Phycochromophyceae (Rabenhorst, 1864) or Cyanophyceae (Sachs, 

 1874), the limits of which were carefully and exactly made out by 

 Stizenberger. It is the name under which the Blue-green Algae 

 have been placed by systematists for many years past, but for 

 some unaccountable reason it has not up to the present been 

 even mentioned in general text-books on botany. 



OCCURRENCE, COLLECTION, AND PRESERVATION OF 

 FRESHWATER ALG^E. 



Algae are universal in their occurrence, no moist situation being 

 without some type of Alga. They are found on damp earth, rocks, 

 walls, palings, tree-trunks, in rain-tubs, etc. ; they are met with in 

 all kinds of running water, from the torrent, waterfall and cataract 



1 Stizenberger in Rabenhorst's Algen Sachsens systematisch geordnet, 1860, p. 17. 



12 



