t 
478 General Notes. [May 
can be easily removed when not nee 
Cheap, and still efficient, cudture-cells for the growth of spores, 
pollen, etc., may be made by the use of the little vulcanite rings 
now sold by all opticians. A ring is fastened to a slide b 
means of gold size; when dry and firm a little oil is spread 
upon the ring, and upon this the cover-glass (bearing the hang- 
ing-drop, in which are the spores) is carefully laid, care being 
taken to secure an air-tight chamber. ; 
Very frequently a student wishes fo preserve a Specimen tem- 
tassic hydrate also. Some of the most satisfactory specimens I 
have ever seen have been obtained in this way. Of course, one 
must have good material to begin with. 
lichens of the genera Collema, Leptogium, or their allies. Any 
one who has previously studied the Nostocs will recognize them 
at once in the lichen sections, where they occur as “ gonidia.” 
One can, in fact, make use of lichens of this kind for supplying 
with certainty good and abundant specimens of Nostoc when the 
Protophytes are under consideration in the laboratory. 
One of the most instructive series of experiments as to the 
water in the plant which the student can undertake consists of 
weighing green Specimens of various kinds, and then, after care- 
ful drying, repeating the weighing to determine the loss of water. 
This can be done very satisfactorily in the winter, when the aie - 
