508 



Journal of Applied Microscopy. 



Tolypothrix. — This form occurs as small tufts, either floating in stagnant water 



or attached to plants and stones. 

 It furnishes an excellent example of 

 false branching. (Fig. 10.) Scy- 

 tonema is a similar form which is 

 fairly common. The glj^cerine 

 method should be employed for 

 permanent preparations, but this, 

 like all small filamentous algae, 

 may be dried on mica for herbari- 

 um purposes. 



B 



Fig. 1 1. Vaucheria. 



A. Vaucheria geminata. B. V. sessilis. 



a. Antheridia. b. Oogonia. 



CHLOROPHYCEAE. 



and 



The ponds, ditches, and rivers of any locality will yield an abundance 

 variety both of the unicellular and multicellular members of 

 this group. The unicellular and filamentous members, to- 

 gether with such forms as Volvox, are best prepared by the 

 glycerine method. The structure is so much more compli- 

 cated than in the Cyanophyceae that it demands far more 

 care and skill to make good preparations. Chromo-acetic 

 acid is a good killing and fixing agent for the whole group, 

 but Flemming's fluid (weaker solution) seems to be a little 

 better in some instances. Very good results have bedn ob- 

 tained by adding about 5 cc. of one per cent, osmic acid to 

 100 cc. of chromo-acetic acid (Schaffner's formula). A for- 

 mula which gives satisfactory results with Spirogyra may 

 cause plasmolysis with Cladophora. The given filament 

 should be placed under the microscope in the fixing agent, 

 and if plasmolysis occurs, the chromic should be weakened 

 or the acetic strengthened until the suitable proportions are 

 determined. This is a slow process, but Cladophora and 

 Vaucheria are almost sure to shrink without it. About 



twenty-four hours in any of 

 the chromic series and a four to ten hours wash- 

 ing in water, will be sufficient for members of 

 this group. Only a few of the most familiar 

 forms will be mentioned. 



Vaucheria.— \X is extremely difficult to get 

 mounts showing the nuclei. The following 

 method is sometimes successful : 



1. Chromo-acetic acid (Schaffner's formu- 

 la), lil hours. 

 Wash in water, 4 to 10 hours. 

 Iron alum, "2 to 4 hours. 

 Water, 15 to 30 minutes. 



Fig. 12. Cladophora. 

 Fixed in cliromo-acetic 

 acid, stained in Haiden- 

 hain '.s iron alum haenia- 

 toxylin. 



Fig. 13. Hydrodictyon. 

 A small portion of a young net. 



2. 

 3. 

 4. 



5. One-half per cent, haematoxylin, over night. 



