Physiology of the Spermatozoa of Ferns. 561 
TABLE IV. Malic acid. 
Concentration 
1*0 
0-05 
0-04 
0.03 
0*02 
O-OI 
O-OOI 
0-0005 
Stimulus 
R 
R 
R 
R-A 
A 
A 
a 
0 
From the results given in the table it will be noticed that 
a repulsion takes place at 0*03 gm per cent. Now Pfeffer 1 
found that if prothallia are placed in a solution of o-oi gm 
per cent, sodium malate the spermatozoa liberated are still 
just observably attracted into the archegonia. He has also 
found 2 that if any solution ^ of the malate be used outside 
a capillary tube as a medium in which the spermatozoa swim, 
then, in order to obtain an observable reaction it is necessary 
to place in the tube a solution = 30 ;tr. When, therefore, he 
finds that if the medium contains o-oi per cent, sodium 
malate, an attraction 3 into the archegonia still takes place, 
we are justified in accepting his conclusion that the least 
concentration of the malate liberated is 0-3 per cent. It may, 
however, be deduced from Table IV that a solution of the 
free acid isomolecular with 0-3 per cent, sodium malate 
strongly repels. It is therefore evident that it is not the 
free acid which plays the chief role in the attraction of 
spermatozoa into the archegonia. It is much more probably 
one or more neutral salts. 
Pfeffer 4 tested various proteids and sugars (see also 
Table IV) and was unable to find any which attracted the 
spermatozoa of Ferns. At present the substances known to 
attract may be classed as organic acids, organic salts and 
inorganic salts. The chemotropism of pollen-tubes offers an 
interesting contrast to the chemotaxis of the spermatozoa. 
Chemotropic deviations are caused by proteids 5 and sugars, 
and as yet no salt or acid has been found to attract. 
Pollen-tubes pass from the stigma to the ovules by growth. 
It should not, therefore, be surprising that the food-stuffs— 
1 Loc. cit., Bd. i, p. 418. 2 Loc. cit., Bd. i, p. 398. 
3 Loc. cit., Bd. i, p. 418. 4 Bd. i, pp. 412-413. 
5 Lidforss, loc. cit., p. 237. 
P p % 
