Journal of Applied Microscopy. 



511 



Zyguema.— Use the same methods as for Spirogyra. In staining conjugating 

 material the stain should be extracted until the four chromatophores of the 

 zygospore become distinct. The nuclei are comparatively small and unsatisfac- 

 tory. The stellate chromatophores are well brought out by alum carmine. If iron 

 alum hgematoxylin and eosin are used, the eosin may well be much deeper than 

 in case of Spirogyra. 



Oe^/ogo;n//m.—In selecting material it will be better for teaching purposes to 



choose the larger monoecious 

 forms. The nuclei, pyrenoids, 

 and chromatophores are easily 

 differentiated. Mayer's hsem- 

 alum is a good stain, especially 

 for the antheridia. Alum car- 

 mine or eosin will bring out 

 the "caps." 



Chara. — This form is so 

 large and coarse that it hardly 

 pays to mount it in glycerine. 

 If a glycerine mount is desired 

 to show the antherida and 

 oogonia in position, spin a ring 

 of cement on the slide, thus 

 making a cell in which small 

 portions of the plant may be 

 mounted. For paraffin sec- 

 tions select the tip of the plant, 

 a piece not more than a quarter of an inch in length. In the smaller species 

 this may show not only the large apical cell, but also various stages in 

 the development of antheridia and oogonia. Delafield's haematoxylin is a very 

 good stain for the apical cell and for the development of ahtherida and oogonia. 

 The later stages in the development of antherozoids are brought out more 

 clearly by the safranin-gentian-violet-orange, or by cyanin and erythrosin. 



Good preparations showing shield, manubrium, capitula, and filaments, may 

 be obtained by staining in bulk in alum carmine and then crushing the antheri- 

 dium under the cover-glass after the specimen is in balsam. 



{To be Continued.) 



Fig. 17. Chara. 

 A. Portion of a branch showing an antheridium, a, and 

 an oogonium, b. B. Median longitudial section of an 

 apical cell. Drawn from a preparation fixed in 

 chromo-acetic acid, and stained in Delafield's hzema- 

 toxylin. 



Growing Anaerobes in Air. 



Anaerobic bacteria (at least in the case of tetanus, symptomatic anthrax, and 

 malignant cedema), grow readily in glucose-agar stick cultures, without any pre- 

 cautions to exclude oxygen, if the tubes be placed in the steam sterilizer for ten 

 minutes, and then quickly cooled just before inoculating, although no growth, or 

 only a scanty one, took place in the same medium under identical circumstances 

 if this precaution was omitted ; the explanation being that the free oxygen is 

 driven out by the heat employed, and growth takes place before the medium has 

 had time to re-absorb sufficient from the air to interfere with growth. 



W. W. Alleger. 



