72 MICROSCOPY FOR BEGINNERS. 



a. Color green, the plant a floating hollow sphere. 



V61VOX (AlffCB, III.). 



a. Color green, the plant not a hollow sphere (5). 



a. Color golden-brown (c). 



1). Cell-wall smooth, rough, warty, or spine-bearing, 

 also soft and flexible; always floating freely, 

 never growing on stems permanently attached to 

 other objects ; a vacuole with swarming granules 

 often present in each end. (Desmids, /.) 



c. Cell-wall marked transversely, often also longitudi- 



nally, by lines, smooth bands, or dots; never 

 spine-bearing ; cell-wall also hard and brittle ; 

 floating freely, or growing on colorless stems 

 permanently attached to other objects. (Dia- 

 toms, II.} 



d. Plants forming cloud-like clusters, long streamers, 



or scum-like floating masses visible to the naked 

 eye ; color bright green or olive, sometimes al- 

 most black ; the cells under the microscope unit- 

 ed end to end to form long, sometimes branching 

 filaments. (Algce, III.) 



1. DfcSMIDS. 



As the desmids are singly invisible to the naked eye, 

 the student can know what he has gathered only after 

 reaching home, except in those rare instances where the 

 little plants have become congregated together in such 

 quantities that a good pocket-lens will show their forms. 

 I have more than once found Clostirium in this profu- 



