50 OF THE DESMIDIACE^E AND SIMILAR MINUTE ALG^E. 



CHAPTER VI. 



OF THE DESMIDIACE.E AND SIMILAR MINUTE ALGiE. 



We naturally pass from the lowly Diatomaceae to their as 

 lowly relations, the Desmidiaceae, since there is so much that 

 is in common between them in regard to their being and 

 their life history, not to mention that the methods of pre- 

 paration for the herbarium are in many respects identical. 



Speaking generally, the Desmids inhabit the same lo- 

 calities with the Diatomaceae, with the single exception 

 that they are an exclusively freshwater family ; not a single 

 species is to be found in the sea. They are to be looked 

 for in bogs, ditches, and ponds, lying in bleak, exposed 

 situations, rarely in shady woods; some, as Closterium, 

 among the filaments of the Oscillatoriae and Conferva? ; 

 others, such as Palmaglasa macrococca, on damp moss, or 

 the surface of wet rocks and cliffs. Boggy heaths, however, 

 are the spots where they mostly congregate, especially where 

 Sphagnum abounds. Swampy places and patches of water 

 scattered over the bog, or shallow drains cut through it, all 

 afford a rich supply of Desmidiaceae. They also love ditches 

 and holes in which, though the water itself is pure, the soil 

 is of a clayey nature ; there they often vegetate in such 

 abundance as to cover the bottom with a dense green film. 



The autumn is the best time of year for collecting these 

 plants, and the outfit necessary is much the same as in the 

 case of the Diatomaceae. 



If the Desmids are in any quantity among the stems of 

 the Sphagnum, the latter will have a slimy, jelly-like feel 

 when grasped. Should the collector, on taking up a tuft of 

 the moss, have reason to suspect their presence, he should 

 let the principal part of the water drain away, though with- 



