No. 413.] REVIEWS OF RECENT LITERATURE. I 
. 413 
Spermatozoa of Ferns.! — This account considerably extends the 
hitherto published work of Pfeffer and others, and is a valuable con- 
tribution to the knowledge of chemotaxis. Buller has found that in 
addition to malic acid and certain malates, experimented with by 
previous authors, other substances also exert a positive chemotactic 
influence on the spermatozoids of ferns. "Various tartrates, oxalates, 
phosphates, and salts of potassium (all substances to be found in cell 
sap) have an attractive influence. Pfeffer’s negative results with 
such substances are ascribed in the case of organic salts to the 
use of too dilute solutions; in inorganic salts to the fact that mix- 
tures (eg. plant ash) were used. Nevertheless, the opinion of 
Pfeffer that it is a malate which attracts the spermatozoid to the 
archegonium in ferns is substantiated, by reason of the high degree 
of concentration required by other salts. Malic acid and its salts 
attract spermatozoids about fifty times more strongly than do other 
substances. That it is not free malic acid which is found in the cell 
sap of the archegonia seems probable in that Pfeffer determined no 
acid reaction in the exudation, and from the fact that malic acid 
alone is decidedly poisonous to the spermatozoids. 
The fact that the diethylester of malic acid is indifferent indi- 
cates an explanation of the chemotactic influence on the basis of 
chemical dissociation, since the afore-named substance is undisso- 
ciated in solution, whereas in malic acid and the malates the nega- 
tive radicle is free as an ion. But at the same time, while it is 
Shown that other undissociable substances, like cane sugar, grape 
sugar, etc., do not attract the spermatozoids of ferns, it is known 
that one at least (i.2., cane sugar) does attract those of the mosses, 
while several attract certain bacterial forms. This fact is men- 
tioned, but no explanation is attempted, beyond suggesting the 
possibility that some undissociable substances may be found which 
do exert a positive chemotactic influence on the spermatozoids of 
ferns. It is then the case, that while certain substances (¢.g., malic 
acid) may be indifferent in an undissociated form, other substances 
attract in some cases, although there is no dissociation of the 
molecule. This would naturally hinder at present the drawing of 
any general conclusions regarding the relation of chemotaxis and 
dissociation. 
The fact that the spermatozoids of Gymnogramme mertensii and 
; Buller, A. H. R. Contribution to our Knowledge of the Physiology of 
the Spermatozoa of Ferns, Annals of Botany, vol. xiv, No. lvi (December, 1900), 
P. 543. 
