CHLOROPHYCEAE 
191 
Use the Venetian turpentine method. In mounting, use small 
scissors freely. You cannot untangle a mat of Vaucheria so as to 
give good views. 
For the development of the oogonium and antheridium, for 
fertilization and for the structure and development of the various 
spores, thin sections are necessary. Imbed in paraffin. For nuclear 
details, use iron-haematoxylin; for cytoplasm, 
use safranin, gentian-violet, orange. 
Cladophora.—'This genus is found in both 
salt and fresh water. The fresh-water forms 
are usually attached to sticks or stones in quiet 
or running water. The mats feel rough and 
crisp and, even under a pocket lens, show the 
characteristic branching by which the form is 
easily recognized. The absence of a mucous coat 
makes Cladophora a convenient host for numer¬ 
ous parasitic algae, among which diatoms be¬ 
longing to the genera Cocconeis and Gomphonema 
are particularly abundant. 
For laboratory cultures, select the forms 
found in quiet water, but for preparations, forms 
growing where the waves dash hard are better, 
since you can get a fine display of branches 
under a small cover. Forms growing in still 
water or in gently flowing water may look like 
unbranched filaments under an ordinary cover. 
The special chromo-acetic-osmic solution is excellent for Cladophora. 
Iron-alum haematoxylin, followed by the Venetian turpentine 
methods, gives the best results for nuclei and pyrenoids. Magdala 
red and anilin blue are better for the cell wall and chromatophores 
(Fig. 43). 
Ulothrix.—Where the problem of the origin and evolution of sex 
is studied, Ulothrix is an indispensable type. Ulothrix zonata is 
found in springs, brooks, and rivers, occurring in bright-green masses 
attached to stones in riffles, especially in sunny places. It is abun¬ 
dant on stones and piles along the beaches of lakes. Nuclear division 
takes place at night, most abundantly about midnight, and is followed 
by a rapid development of zoospores and gametes, which continue 
to be discharged throughout the forenoon. In the afternoon the 
Fig. 43.— Cladophora: 
fixed in chromo-acetic acid 
and stained in iron-alum 
haematoxylin. 
