50 OF THE DESMIDIACEjE AND SIMILAR MINUTE ALGjE. 
CHAPTER VI. 
OF THE DESMIDIACEjE AND SIMILAR MINUTE ALGA2. 
We naturally pass from the lowly Diatomacese to their aa 
lowly relations, the Desmidiaceas, 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 Diatomacese, 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 Oscillatoriaj and Confervse ; 
others, such as Palmagkea 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 Desmidiace^e. 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 Diatomacese. 
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- 
