164 



MORPHOI.OG 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 

 sUmy 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 

 R °^ 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 fin the genera Antho- 

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

 and in the j)erforated cells of Sphagnum 

 acutifolium. Anab;ena is another common 

 and widely distributed genus. The species 

 occur in fresh or salt water, singly or in slimy 

 Anabaina azoUae lives endophyti- 

 cally in the leaves of the water fern, Azolla. 



filanu'iit 



Fig. T70. 

 Nostoc linckii. A, 

 with two heterocysts (/i), and a masses, 

 large number of spores isp) . 

 B, isolated spore beginnin^^ to 

 germinate; C, young filament 

 developed from spore. (After 

 Bomet. ) 



Class Schizomycetes. 



357. Bacteriales. — The bacteria 

 phycea, under the name Srhizophy 

 omycetes, or fission fungi, because 

 many of them multii)lv bv a divis- 

 ion of the cells justas the blue-green 

 algae do. For example, liacillus 

 forms rods which increase in length 

 and divide into two rods, or it may 

 grow into a long thread of man\- 

 short rods. Micrococcus consists 

 of single rounded cells. Stre]ito- 

 coccus forms chains of rounded 

 cells, Sarcina fc)rms irregular cubes 

 of rounded cells, \vbilr iilhci's like 

 Spirillum arc spiral in funn. 

 Bacillus subtilis niav be obtained 



arc sometimes classified with the Cvano- 

 ta, and represent the subdivision Schiz- 



Fig. 171. 

 Bacteria. A, Bacillus subtilis. Spores 

 in threads, unstained rods, and stained rods 

 showing cilia; B, Bacillus tetani, the teta- 

 nus or lockjaw bacillus, found in garden 

 soil and on old rust\' nails. Spores in club- 

 shajied ends. C , Micrricocctis; D, Sarcina; 

 /■., StrcjilMCMCcus; F, Spirillum, {After 

 MiMula.l 



by making an infusion from hay and 



