CHLOROPHYCEAE 
175 
results, the fruiting condition may be induced in many of the common 
laboratory types. Knop’s solution will be needed in most cases. 
A stock solution which can be diluted as required may be made as 
follows: 
Potassium nitrate, KN0 3 . 1 g. 
Magnesium sulphate, MgS0 4 . 1 g. 
Calcium nitrate, Ca(N0 3 ) 2 . 3 g. 
Potassium phosphate, K 2 HP0 4 . 1 g. 
Dissolve the first, second, and fourth ingredients in 1 liter of 
distilled water, and then add the calcium nitrate. A precipitate of 
calcium phosphate will be formed. For practical purposes this may 
be called a 0.6 per cent solution. Whenever a dilute solution is 
made from the stock solution, the bottle must be shaken thoroughly 
in order that a proper amount of the precipitate may be included in 
the diluted solution. To make a 0.1 per cent solution, add 5 liters of 
distilled water to 1 liter of the stock solution; for a 0.3 per cent solu¬ 
tion, add 1 liter of distilled water to 1 liter of the stock solution, etc. 
The addition of a liter of a 0.2 per cent solution to 4 or 5 liters 
of water will often produce a more thrifty growth. Directions for 
inducing reproductive phases are given in connection with the various 
types. With a good supply of glass jars, plenty of Knop’s solution, 
a reasonable control over temperature, and the teacher’s usual 
amount of patience, most laboratory types can be studied in the 
living condition at all seasons of the year. 
Collecting algae need not be so laborious as most botanists make 
it. Forms like Spirogyra, Zygnema, Cladophora, Vaucheria , and 
Hydrodidyon may be rolled up in wet newspaper and carried in a 
botany can. They suffer less from lack of water than from lack of 
air. Large quantities of material can be brought in and transferred 
to water after reaching the laboratory. Even after 24 hours in the 
wet paper, such forms seem to suffer no damage. 
Permanent preparations are needed to show details which are 
not so evident in the fresh material. The unicellular and filamentous 
members, together with such forms as Volvox, are best prepared by 
the Venetian turpentine method. The structure is so much more 
complicated than in the Cyanophyceae that it demands far more care 
and skill to make good preparations. 
In many, probably in most of the green algae, nuclear and cell 
division takes place at night. This is definitely known to be the case 
