1899 | CURRENT LITERATURE 441 
THE RUST FLORA of California, according to E. W. D. Holway in the 
October Evythea, embraces 122 species of Puccinia, 42 of Uromyces, and 73 
of other genera.—J. C. A. 
ANOTHER ARTICLE™ has recently been added to the valuable series of 
physiological papers already so auspiciously inaugurated by Dr. Klebs. The 
same ingenious accurate experimentation which characterized the earlier 
papers of the series is evident. The presentation is masterly. The purpose of 
the research is to determine the chemical and physical factors which incite or 
alter the various modes of reproduction in Saprolegnia mixta. It is found 
that this species will grow indefinitely without either sexual or asexual repro- 
duction if nourishment be abundant; but at any time the extensive formation 
of zoospores can be incited by simply starving the hyphe, e. £., by placing 
them in water. By noting the maximum concentration at which various foods 
induce the formation of zoospores an idea was obtained as to their relative 
food value. Albumens are rich; amido-acids can furnish C as wellas N ; in 
general the food value rises with the carbon content; glucosides vary from 
toxic to indifferent or even favorable; inorganic acids ani their salts are of 
but little value. 
By varying the nutritive value of any medium the fungus can be made at 
will to assume a purely vegetative condition; to produce rudimentary spo- 
fangia ; to form sporangia which bear zoospores that do not escape 3 and to 
produce functional zoospores. All of these phenomena depend for their exist- 
€nce upon the concentration of the medium, not upon the total quantity of 
nutriment. 
strong solutions the formation of zoo- 
It happens, however, that even in 
led Dr. Klebs to infer the pres- 
Spores is often eventually suppressed. This 
ence of an inhibiting agent formed in the medium by the growth of the fungus. 
One such substance he finds is ammonium carbonate. If the mediuts be 
rendered weakly acid zoospore formation can be resumed. Starvation, if very 
§tadual, causes the mycelium to become too weak to build zoospores. Poisons 
inhibit their formation as does also. high osmotic pressure. 
very clearly what are the necessary relations and also the responses, but the 
Teasons for both are totally obscure. Zoospores are never found unless oe 
tips of the hyphz are in contact with water. Oxygen, light, and heat are 0 
little importance. 
If a well nourished mycelium be placed in a poor m 
ditions render the formation of zoospores impossible, ¢. om 
Sexual organs will soon appear in abundance. These, however, are eee . 
to heat (their maximum being 26°, that of sporangia 32°) and fastidious a 
“Zur Physiologie der Fortpflanzung einiger Pilze: Jahr. 
1899. Reviews of earlier papers may be found in this journal 23 : 21 
77. 1899. 
edium where the con- 
ina solid medium, 
f, wiss. Bot. 33: 71- 
4. 1893, and 27: 
