246 PART IV. CLASSIFICATION. 



the evidence is at present inconclusive. No form of sexual repro- 

 duction has been observed in any member of this sub-class. 



The cells of the Cyanophycese contain nuclear substance, but 

 the nucleus is not well-defined ; and the chlorophyll and the phy- 

 cocyanin appear to be diffused throughout the cytoplasm, and not 

 to be aggregated in special plastids. 



The Cyanophycese resemble the Schizomycetes, among the Fungi, 

 in many respects ; as, for instance, in their general form and struc- 

 ture, in their vegetative multiplication, in their spore formation, 

 in the absence of sexual reproduction, in the formation of a bulky 

 mucilaginous cell-wall, and in their polymorphism. On these 

 grounds they are frequently placed, along with the Schizomycetes, 

 in a distant class Schizophyta. But this arrangement does not 

 seem to secure any special advantage. It is more natural to regard 

 the Cyanophycese and the Schizomycetes as parallel groups, the 

 one belonging to the Algse, the other to the Fungi. 



The Cyanophycese are both marine and fresh -water : many grow 

 on damp walls, rocks, etc. 



Sub-Class IL CHLOROPHYCE.E, or Green Algae. In the simpler 

 forms the plant consists of a single cell (e.g. Protococcoidese, some 

 Desmidiese): or it is coenocytic, as in the Siphonoidese, either 

 unseptate (Siphonacese) or incompletely septate (Cladophoracese, 

 Hydrodictyacese) ; it is, in fact, only in this sub-class that the 

 coanocytic structure occurs among the Algse : or the body is mul- 

 ticellular, with essentially similar cells and therefore coenobitic 

 (e.g. Spirogyra, Pandorina, Ulva), or exhibiting at least a dis- 

 tinction between vegetative and reproductive cells (e.g. Volvox). 

 The only members of the sub-class in which there is any appreci- 

 able differentiation of the vegetative cells are the Characese. 



The body presents all degrees of morphological differentiation ; 

 it may be a thallus, either spherical (e.g. Hsematococcus, Volvox), 

 or filamentous (e.g. Spirogyra, Ulothrix), or a flattened expansion 

 (e.g. Diva, Coleochsete) ; or a filament with rudimentary differen- 

 tiation into root and shoot (e.g. (Edogonium) ; or it may present 

 differentiation into stem, leaf, and root (e.g. Characese). It may 

 be free or attached. Growth and cell-division commonly go on in 

 all the cells of ,the body, so that the growth is intercalary (e.g. 

 Spirogyra, (Edogonium, Ulva) ; it is but rarely that there is a 

 definite growing-point, and then it is apical (Coleochsete, Characese, 

 -some Siphonoidese) ; and in the cellular plants which have an 

 apical growing-point, there is a single apical celL 



