1910] CURRENT LITERATURE 73 
upon the abundance of the water supply. Assuming that free water was a very 
important agent in the origination of living matter, the development of the gameto- 
phytic stage of plant life is shown to be dependent upon the same factor. As 
aridity was encountered over extended land areas, the stress thus produced led 
to the development of the sporophyte with its vascular system and finally its 
seed habit. The earlier geological strata from arid areas contain no plant fossils, 
because at that period vegetation was characterized by the predominance of 
plants with separate gametophytes. Cycads and Bennettitales were the first 
plants to show xerophytic structures, and from their beginning the history of 
desert forms may be traced. Aridity, causing the reduction of surface area and 
the thickening of tissues, has evolved spinose and switchlike forms; while in the 
regions of most extreme aridity this evolutionary development has gone much 
farther, with the development of remarkable storage structures in leaf and stem 
organs. These succulent xerophytes representthe highest degree of differentia- 
tion in seed plants, and are found most abundantly in the very arid regions of 
the Karoo in South Africa, in the deserts of Brazil and Chili, in the arid regions 
of southern Mexico, and in the Sonoran and Chihuahuan deserts.—Gero. D. 
ULLER. 
Algae in the laboratory.—Teachers will be interested in the practical methods 
which have made NreUWLAND’s so successful in growing algae in the laboratory. 
Large aquaria are not necessary, the best results often being obtained with gallon 
or two-gallon jars. The commonest mistake is to change the water, even the 
single change usually involved in bringing algae from the field to the laboratory 
often being disastrous. It is safer to bring the water in which the plants are grow- 
ing. When necessary to renew the water, not more than one-fifth the volume 
should be added, and tap water should be allowed to run for a moment to avoid 
the introduction of undesirable salts. Bacterial decomposition is best prevented 
by introducing only a small amount of material, not more than one cubic inch to 
the gallon. As the material grows, the increasing amount can be accom- 
modated because of the developing adaptation to the environment. A few plants 
of Chara are often desirable, since they prevent the water from becoming too 
hard, and a little Utricularia will rid the culture of undesirable animal life. 
When the algae disappear, the culture should-not be thrown out, for the forms 
usually reappear after a time. Mud and sticks from spots where algae have been 
noticed may be brought into the laboratory in midwinter and soon yield vigorous 
Cultures. Detailed directions are given for securing and keeping many of the 
Most desirable laboratory types.—CHARLES J. CHAMBERLAIN. 
A new maize from China.—The Department of Agriculture has been investi- 
Sating a new type of corn received from near Shanghai, China, in March 1906, 
Op usar eas . 
*S NIEUWLAND, J. A., Hints on collecting and growing algae for class work. Mid- 
land Naturalist 1: 85-97. 1909. 
