544 
has recently studied more carefully the 
nuclear division, but on account of the 
large number of the chromosomes was not 
able to determine whether or not a reduc- 
tion takes place. He points out, as others 
have done, the similarity in the process of 
the formation of the conjugating cells of 
Basidiobolus and Mougeotia among the 
Mesocarpee, and to these there might be 
added the case of Sirogonium in which the 
paternal cell just prior to copulation under- 
goes division. The division of the copula- 
tion cell in Basidiobolus, Mougeotia, Siro- 
gonium, ete., suggest at least some sort of 
preparatory act, but whether this is for the 
purpose of a quantitative reduction of the 
kinoplasm, as Strasburger thinks sometimes 
takes place, or is a real reduction in the 
number of the chromosomes. must be de- 
termined by further study, so that the bear- 
ing of these experiments on the question of 
a reducing division must for the time be held 
in reserve. 
One of the very interesting fields for ex- 
perimental investigation is that of the cor- 
relation processes which govern the mor- 
phology of the sporophylls (stamens and 
pistils) of the Spermatophyta. One of the 
controlling influences seems to be that of 
nutrition, and in thi$ respect there is some 
comparison to be made with the correlative 
processes which govern the determination 
of sex in plants. ; 
Among the ferns and some others of the 
Pteridophyta a number of experiments have 
been carried on by Prantl, Bauke, Heim 
(96), Buchtien (’87) and others to deter- 
mine the conditions which influence the 
development of antheridia and archegonia. 
Prantl found that in prothallia of the ferns 
grown in solutions lacking nitrogen there 
was no meristem and consequently no ar- 
chegonia, while antheridia were developed, 
but if the prothallia were changed to solu- 
tions containing nitrogen, meristem and 
archegonia were developed. All the experi- 
SCIENCE. 
mented especially with Vaucheria, 
[N.S. Vou. VI. No. 145. 
ments agree in respect to nutrition; with 
scanty nutrition antheridia only were de- 
veloped, while with abundant nutriment 
archegonia were also developed. Heim 
studied the influence of light and found 
that fern prothallia grow best with light of 
20%-25%. Exclusion of the ultra violet 
rays does not affect the development of the 
sexual organs. He argues from this that 
the ultra violet rays are not concerned in 
the elaboration of the material for flower 
production as Sachs had suggested. In 
yellow light the prothallia grew little in 
breadth ; they also grew upward, so that 
few of the rhizoids could reach the sub- 
stratum. Antheridia were here very nu- 
merous. After seven months these pro- 
thallia were changed to normal light, and 
in four months afterward archegonia were 
developed. 
Among the algze Klebs (’96) has experi- 
such 
species as V. repens and JV. ornithocephala, 
where the antheridia and oogonia are de- 
veloped near each other on the same thread. 
With weak light, especially artificial light, 
the oogonium begins first to degenerate. 
He never succeeded in suppressing the 
antheridia and at the same time in produc- 
ing oogonia. 
High temperature, low air pressure or 
weak light tend to suppress the oogonia, 
and at the same time the antheridia may 
increase, so that the number in a group is 
quite large, while the oogonium degenerates 
or develops vegetatively. Klebs concludes 
from his experiments that the causes which 
lie at the bottom of the origin of sex in 
Vaucheria, as in other organisms, are 
shrouded in the deepest mystery. In the 
higher plants a number of experiments have 
been carried on for the purpose of learning 
the conditions which govern the production 
of staminate and pistillate flowers, or, in 
other words, the two kinds of sporophylls. 
From numerous empirical observations on 
