510 



Journal of Applied Microscopy. 



stained with eosin. 

 twenty-four hours. 



Zygnema. 



The eosin (one per cent, aqueous solution) should act for about 

 Then transfer to one per cent, acetic acid for a few minutes. 

 If the stain comes out rapidly in the acid, one minute 

 may be sufificient, but if the stain does not wash out, it is 

 better to let the acid act for four or five minutes. Wash 

 thoroughly in water to remove all trace of acid, or the 

 preparation will fade. Transfer to ten per cent, glycerine 

 and proceed as usual. 



Spirogyra. — This is probably the most widely known 

 of all the algae, and, fortunately, it is rather easy to obtain 

 beautiful and instructive preparations. The following is 

 a good fixing agent for most Spirogyras : 

 Chromic acid, ^ gram. 

 Glacial acetic acid, y^^ gram. 

 Water, 99 cc. 

 The addition of one cc. of osmic acid seems to im- 

 prove it without causing any blackening. Flemming's 

 weaker solution is excellent. If it causes too much 

 The filament at the left shows blackening, as it probably will, the material, after being 



three zygospores and one i j , i j i , j • , • i r i j 



parthenogenetic spore which washcd, sliouid bc piaccd m wcak pcroxide ot hydrogcn 



is distinguished by having . 



only two chromatophores. (onc part H„Or, to thrcc parts HoO) Until the blacken- 



The filament on the right ^ ^ , ^ ^ ^ - / 



shows two cells, each with a ing duc to osmic acid disappears. After a moment's 



pair of stellate chromatoph- . . . . 



ores. Drawn from material washmg m Water it is then ready for the stain. The iron 



fixed in two per cent, formalin . ... , . 



and stained in iron alum alum hffimatoxylm, as just described, brings out the nuclei 



haematoxylin. . ""^ . . . 



and pyrenoids with great distinct- 

 ness. A few minutes in aqueous eosin after the last wash- 

 ing in water, often gives a beautiful differentiation, but the 

 preparations will be quite inferior if the eosin is allowed to 

 stain too deeply. Mayer's haimalum is a better stain for 

 stages in conjugation. 



It is difficult to get Spirogyra into paraffin without 

 shrinking, but it can be done. Watch carefully and note 

 where plasmolysis occurs. There will probably be little or 

 no trouble until the transfer from 100 per cent, alcohol to 

 the clearing agent. Make this transfer as gradual as may 

 be necessary. After the pure xylol or other clearing agent 

 is reached, add a lump of paraffin large enough to saturate 

 the clearing fluid at a temperature of 40 to 45 degrees C. 

 Allow the xylol to evaporate at this temperature and imbed 

 as usual, taking care to keep the filaments as nearly parallel 

 as possible. Many elegant combinations, like cyanin and 

 erythrosin, fuchsin and iodine green, safranin-gentian-violet- 

 orange, and others not available for glycerine preparations, Fig. i6. Oedogonium 



1 1 . , rr • T ■ ■ , nodulosum. 



can be used with paraffin sections. It is comparatively easy ^ Antheridia. b. Oogoni- 

 to get any such alga into celloidin. Safranin and Dela- JI^Ted ^^rone°pe7Tent. 

 field's haematoxylin then makes a good combination. i^Zjer'stimahim."'"''^ 



