1886.] BOTANICAL GAZETTE. 149 
elusive, the result of long tramps, the reward of perseverance, long-suffering, 
and other kindred virtues. A collector of desmids needs to be provided with a 
large stock of patience, considerable endurance, and some courage, a pair of 
rubber boots, and vials ad libitum. 
Except the most common forms of Closteria and Cosmaria, they particu- 
larly affect clear pure water. For instance, a summer’s search in Dakota was 
fruitless on account of the alkaline water. Strong currents are also unfavor- 
able to their deposition. I have made my best “finds” in small pools or ponds, 
fed by springs, or connected with larger lakes by underground channels, such 
water being pure and undisturbed by currents or waves. 
mids sometimes form a delicate green film on the banks or bottom of a 
pool, in which case they can be gently urged by the help of a spoon into a wide- 
necked bottle; but more commonly they can be found clinging to the stems 
and leaves of aquatic plants, such as Vallisneria, Anacharis, Myriophyllum, 
with me to produce desmids in abundance. They can be stripped from the 
leaves by the hand, or, better still, the moss can be gathered, being careful to 
dislodge as little mud as possible, and washed thoroughly in water. When the 
sediment has settled pour off the superfluous water. Your microscope may 
show the remainder to be a rich harvest of such inexpressibly rare and beauti- 
ful forms as to make one forget all fatigue and vexation.—ELoisre BUTLER. 
Nostoc Group (PHycocHroMace#).—Thin gelatinous species, which form 
expansions on the ground or on rocks, are prepared by removing them with 
small portions of the substance to which they are attached and allowing them 
to dry-under slight pressure between plates of glass or other hard substances to 
which they will not adhere. The smaller and more delicate aquatic species 
should be floated out on pieces of mica or glass and dried in the air, but not ex- 
posed to strong sunlight. They may also be floated out on paper like larger 
alge, but, before pressing, they should be allowed to dry a few hours in the air. 
In the press they should be covered with thin unglazed cloth as in the case of 
alge. Species like Oscillarie, which have a vibratory notion, may be placed 
in a large drop of water on a moistened paper, and left over night. In the 
morning the threads will have separated from ther so that the specimen 
has expanded into a circular shape and the threads have arranged themselves 
but they sometimes are a good while in drying. Prepared in this way they are 
not unfrequently considerably distorted, and it is well to keep a few specimens 
rough dried for. study. On remoistening they swell to nearly their original 
Proportions. Specimens preserved in alcohol or glycerine are of little value.— 
W. G. Farrow. 
Strme Mops (Myxomyceres).—The excellent account of the methods of 
collecting and preserving this class of plants given by Dr. Geo.” A. Rex in this 
journal a year ago makes it superfluous to go over the ground again. We, 
however, desire to call attention to a superior manner of preserving mater: 
