186 
METHODS IN PLANT HISTOLOGY 
amount taken up by the water while standing in the water pipe being 
detrimental. 
The species found in running water will usually conjugate within 
a week when brought into the laboratory and placed in rain water or 
tap water. Species belonging to quiet waters, when brought into 
the laboratory and placed in a 0.2 per cent Knop’s solution, are 
likely to undergo rapid cell division and growth. After the alga 
has remained in such a culture for a few days or for a week, conjuga¬ 
tion may be induced by transferring to rain water or tap water, and 
Fig. 40.— Scenedesmus: photomicrograph from a preparation by Dr. Yamanouchi, mounted 
whole and stained as described in the text; Cramer contrast plate; 4-mm. objective; ocular X4; 
yellowish-green filter; camera bellows, 1 meter; arc light; exposure, 6 seconds. X675. 
keeping the culture in bright sunlight. Conjugation may begin 
within 3 or 4 days. Variations in temperature between 1° and 15° C. 
have little influence upon conjugation. 
The special chromo-acetic-osmic solution fixes well. Stain some 
material in iron-alum haematoxylin and some in Magdala red and 
anilin blue. Use the Venetian turpentine method, and on each slide 
mount material stained in both ways. With Magdala red and anilin 
blue the spiral chromatophore takes the blue and its pyrenoids the 
red. If the material contains figures, stain in iron-haematoxylin. 
This will stain the figures, but will hardly touch the chromatophore 
