586 MICROSCOPIC FORMS < >F VEGETABLE LIFE THALLOPHYTES 



constriction between the two halves of the cell, the division of its 

 margin into segments by incisions more or less deep, and its exten- 

 sion into teeth or spines. 



The Desmidiacece are not found in running' streams, unless the 

 motion of the water be very slow, but are to lie looked for chieflv 

 in standing waters. Small shallow pools that do not dry up in 

 summer, especially in open, exposed situations, such as boggy 



moors, are most productive, 

 commonlv lie at the bottom of 



IMC. 440. Binary subdivision and conjugation of 



The larger and heavier species 

 the pools, either spread out as a 

 thin gelatinous stratum, 

 or collected into finger 

 like tufts. By gently 

 passing the fingers be- 

 neath these they may be 

 caused to rise towards the 

 surface of the water, and 

 may then be lifted out by 

 a tin box or scoop. Other 

 species form a slimy 

 stratum floating on the 

 surface of bog- pools, or a 

 greenish or dirty cloud 

 upon the stems and leaves 

 of other aquatic plants ; 

 ;ii id these also are best 

 detached by passing the 

 hand beneath them, and 

 'stripping' the plant be- 

 tween the fingers, so as to 

 carry off upon them what 

 adhered to it. If. on the 

 other hand, the bodies of 

 which we are in search 

 should be much diffused 

 through the water, there 

 is no other course than to 

 take it up in large quanti- 

 ties bv the box or scoop 



Itrxtiiidiuni cijliudricuni : A, portion of filament, and to separate them hv 

 surrounded bv gelatinous envelope : B, dividino fi i ' 



cell; C, sn.gle cell viewed transversely; D, two* Draining through a piece 



cells in conjugation ; E, formation of zygospore. 



of linen. At first, nothing 

 appears on the linen but 

 a mere stain or a little dirt; but by tne straining of repeated 

 quantities a considerable accumulation mav be gradually made. 

 then be scraped oil' with :i knife, and transferred 

 with fresh water. If what has been brought up 

 richly charged with these forms, it should be at 

 bottle; this at first seems onlv to contain 



a 



This should 

 into bottles 

 by hand IK 

 cnee deposited in a 

 foul water: but bv 



little time, the 

 the water mav 



allowing it to remain undisturbed for 



desmids will sink to the bottom, 

 then he poured oil', to he replacet 



most of 

 a fresh 



