Physiology of the Spermatozoa of Ferns . 549 
tures. The oversight was rendered all the easier by the 
relatively strong attraction of malic acid. It was indeed 
when experimenting with five gm per cent, potassium nitrate 
that I discovered an attraction by this substance, and was 
thereby led to make further investigations. 
As a result of my work several of Pfeffer’s conclusions must 
undergo modification. Considerable additional probability 
seems, however, to be given to the supposition that malic acid 
(in the form of a salt) plays the chief r 61 e in the attraction of 
spermatozoa into the archegonia of Fern-prothallia. 
When the work was near completion I came to the con¬ 
clusion that light might be thrown upon the results by an 
application to them of the electrolytic theory of dissociation 
of solutions. 
Material and Methods. The spermatozoa employed 
were exclusively those from the prothallia of Gymnogramme 
Martensii . Leaves of this Fern were plucked and allowed to 
dry on sheets of paper. The spores so collected were then 
sown in pots on a substratum of peat mixed with a little sand 
and soil. The pots were set in a glass case (about 3 x 2 x 1 ft.) 
which was situated in a moderately warmed greenhouse and 
shaded from the direct rays of the sun by shrubs. The air 
in the case was kept saturated with water vapour. 
The spores were usually sown thickly together. When 
this was so, the prothallia developed a relatively large number 
of small antheridia. When the spores had been more scattered 
the prothallia became larger, heartshaped and with relatively 
less numerous although larger antheridia. The smaller anther¬ 
idia contained fewer spermatozoa, sometimes only eight or 
twelve, while the largest contained as many as sixty-four. 
When a pot was found to contain prothallia which had 
produced sufficient antheridia it was brought into the labora¬ 
tory and placed under a large bell-jar, which was manipulated 
in such a way that the prothallia continued to grow in 
relatively dry air. This appears to enable the antheridia to 
one case would help to obscure the effect, for this substance does not attract. 
(Vide infra, Table I.) 
