548 Bidler.—Contributions to our Knowledge of the 
mitted. Sodium maleate was determined to give a much 
weaker stimulus 1 than sodium malate. It was also pointed 
out that it is doubtful if maleic acid and its salts occur in 
plant-cells while on the other hand malic acid is often abun¬ 
dant in cell-sap, and was shown to occur in a decoction 2 of 
prothallia. 
As a result of his work Pfeffer came to the well-known con¬ 
clusion 3 that it is most highly probable that on the bursting 
of the archegonia malic acid is the substance liberated which 
attracts the spermatozoa to the oospheres. 
Voegler 4 has since determined that malic acid, sodium, 
potassium, ammonium, magnesium and calcium malates give 
approximately equal attractions. He has also repeated those 
experiments of Pfeffer according to which the diethylester 5 of 
malic acid appears to act indifferently. 
During some work upon the spermatozoa of Ferns I have 
discovered that a number of other substances beside malic 
acid exert an attractive stimulus. These include organic and 
inorganic salts (e. g. those of potassium, tartrates, oxalates 
and phosphates) commonly found in cell-sap. I have com¬ 
pared the stimulus given by about forty different substances, 
with the remarkable result that the strongest attraction has 
been found to be given by malic acid and its salts. 
The negative results of Pfeffer appear to be due to the fact 
that his solutions of organic salts 6 were not sufficiently con¬ 
centrated,while conclusions were drawn concerning the stimulus 
given by inorganic salts 7 from the effect observed with mix- 
1 Loc. cit., Bd. i, compare pp. 379-81 and p. 382. 
2 Loc. cit., Bd. i, p. 417. 
3 Loc. cit., Bd. i, p.417 among others. This conclusion may be received ‘mit 
einer an Gewissheit grenzenden Wahrscheinlichkeit 5 that it is true. 
4 Voegler, Beitrage zur Kenntniss der Reizerscheinungen. Bot. Zeit., Jahrg. xlix, 
1891, p. 659. 
5 Voegler, loc. cit., p. 659. Pfeffer, loc. cit., Bd. ii, p. 655. 
6 Pfeffer, loc. cit., Bd. i,p. 411. The concentrations used were between 0.05 and 
0-15 gm °/ 0 . Spermatozoa are either indifferent to or but very slightly attracted 
by these solutions. 
7 Loc. cit., Bd. i, p. 410. Solutions were made from the ashes of an extraction 
from grass. The concentration is not stated. The ammonium nitrate added in 
