164 



MORPHOLOG Y. 



the soil at the bottom of the pool, and as gas becomes entangled in the mat 

 of threads, it is lifted from the bottom and floated to the surface of the water. 

 The plant is thread-like, and divided up into many short cells. The 

 threads often show an oscillating movement, whence the name Oscillatoria. 

 356. Family Nostocaceae. This family is represented by Nostoc, which 

 forms rounded, slimy, blue-green masses on 

 wet rocks. The individual plants in the 

 slimy ball resemble strings of beads, each 

 cell being rounded, and several of these ar- 

 ranged in chains as shown in fig. 170. Here 

 and there are often found larger cells (hetero- 

 cysts) in the chain. Nostoc punctiforme 

 lives in the intercellular spaces of the roots 

 of cycads (often found in greenhouses), and 

 in the stems of Gunnera. N. sphaericum 

 lives in the spaces between the cells in many 

 species of liverworts (in the genera Antho- 

 ceros, Blasia, Pellia, Aneura, Riccia, etc.), 

 and in the perforated cells of Sphagnum 

 acutifolium. Anabsena is another common 

 and widely distributed genus. The species 



occur in fresh or salt water, singly or in slimv 



Nostoc hnckii. A , filament J , 



with two heterocysts (h), and a masses. Anabaena azollae lives endophyti- 



germinate; C, young filament 

 developed from spore. (After 



Bomet.) 



Class Schizomycetes. 



357. Bacteriales. The bacteria are sometimes classified with the Cyano- 

 phycea:, under the name Schizophyta, and represent the subdivision Schiz- 

 omycetes, or fission fungi, because 

 many of them multiply by a divis- 

 ion of the cells justas the blue-green 

 algae do. For example, Bacillus 

 forms rods which increase in length 

 and divide into two rods, or it may 

 grow into a long thread of many 

 short rods. Micrococcus consists 

 of single rounded cells. Strepto- { 

 coccus forms chains of rounded ^ 



cells, Sarcina forms irregular cubes soil and on old rusty nails. Spores in club- 

 .. , ... shaped ends. C, Micrococcus; D, Sarcina. 



of rounded cells, while others like E streptococcus; F, Spirillum. (After 

 Spirillum are spiral in form. Migula.) 

 Bacillus subtilis may be obtained by making an infusion from hay and 



Fi 8- I ~ I - 



Bacteria. A, Bacillus subtihs. bpores 

 threads uns tained rods, and stained rods 



