1906] CURRENT LITERATURE 77 
the spermatozoid, however, may continue for ten or fifteen minutes, and of the 
cilia for five minutes longer. PFEFFER’s capillary method was used in the experi- 
ments. The principal headings are: position chemotaxis, relation between the 
intensity of the stimulus and extent of the reaction, repulsion by free acids and 
alkalis, negative chemotaxis with the ions of heavy metals, repulsive effect of 
alkali salts, behavior with osmotically acting substances, repulsive effect of ions 
of certain organic acids, the action of narcotics, theoretical, and review. 
Malic acid acts as a strong topochemotactic stimulus and may be regarded as 
the specific stimulant for the spermatozoids of Isoetes, although certain other 
substances also exert some topochemotactic influence. Free malic acid in weak 
solutions exerts a positive chemotactic influence, but in stronger solutions a nega- 
tive one. The salts of various metals act as negatively chemotactic stimuli, as do 
also the anions of di- and tribasic organic acids, including malic acid. The 
positive chemotaxis with malic acid is of a typically topotactic nature. The 
reaction consists in a turning of the body axis of the spermatozoid and a movement 
toward the source of stimulation. Whether the structure for the perception of 
chemotactic stimuli consists of the whole body of the spermatozoid or only of 
localized portions of it is not yet determined.—C. J. CHAMBERLAIN. 
Tuberization.—The causes of tuberization still furnish a field for study. 
BERNARD first supposed that Fusarium Solani was the endophytic fungus of the 
potato; this has since been disproved by GALLAUD and by BERNARD himself, but 
the identity of the fungus is still undetermined. H. Jumette® has been con- 
ducting experiments on Solanum Commersoni, a tuber-bearing species related to 
the potato, but as yet his results are largely negative. The chief interest attached 
to his studies are occasioned by the fact that S. Commersoni has small slowly 
developing tubers placed on long stolons; these are the very characters which the 
potato is said to have had when first introduced into Europe, before the endo- 
phytic fungus became sufficiently abundant. S. Commersoni was infected by 
fungi from S. tuberosum, but, as stated above, with negative results. JUMELLE 
thinks that with suitable infection, it may be possible to secure tubers like those 
of the potato, and further experiments are in progress. It should be said that 
GALLAuD thinks that BERNARD has not yet isolated the true tuber-forming 
fungus.—H. C. Cow es. 
Two parasitic fungi—KirBaHNn'? has worked out the life histories of two 
common species of the so-called Imperfecti group. The first of these is the 
common elm fungus, Phleospora Ulmi (Fr.) Wallr. This is connected with an 
ascomycetous form, which appears on the infected dead leaves during the 
winter and ripens in spring, when the spores are ejected and infect the young 
9 JuMELLE, H., Del’influence des endophytes sur la tubérisation des Solanum. 
Rev. Gén. Bot. 17: 49-59. 1905. 
to KLEBABN, H., Untersuchungen iiber einige Fungi im perjecti unddie ea 
Aivtalapeles Rais I. u. Il. Jahrb. Wiss. Bot. 41: 485-560. figs. 75. 
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