1899] ORIGIN OF THE LEAFY SPOROPHYTE 47 
progressive antithetic alternation.” He calls attention to the 
remarkable constancy of alternation in this group, apogamy and 
apospory being singularly absent. This undeviating alternation 
he suggests may be accounted for by the dependence of the 
sporophyte, which is in an ‘‘equable physiological condition.” 
As a contrast to this, the independence of the pteridophyte 
sporophyte, and its exposure to varied conditions, may have 
caused more freely unusual developments. The primitive pteri- 
dophyte, however, was probably in a dependent condition, as the 
embryos of modern pteridophytes are. 
Apogamy and apospory Professor Bower would regard as 
“abnormalities,” calling attention to the fact that these phenom- 
ena have their ‘“‘headquarters” in the leptosporangiate ferns, a 
peculiarly specialized phylum with many other abnormalities. 
Even when apogamy occurs the archegonia are first produced, 
indicating the “first intention” of the plant; and in both apog- 
amy and apospory the growths may be very anomalous. 
In this connection, Professor Bower makes a very interesting 
Suggestion, based upon the experiments of Dr. Lang and others. 
He observes that apogamy is induced by prevention of contact 
with fluid water (‘rendering fertilization impossible”), exposure 
to direct sunlight, and possibly to certain temperature conditions. 
All this leads to a ‘‘plethoric”’ state, which he thinks may be a 
necessary condition preceding apogamy, as opposed to deficient 
nutrition, which precedes apospory, the latter being ‘‘a physio- 
logical tefuge for the destitute plant.’’ He suggests that nuclear 
changes may accompany these conditions, plethora doubling the 
chromosomes, and hence inducing the development of a sporo- 
phyte ; and deficient nutrition reducing the chromosomes, thus 
making a gametophyte possible. Of course it remains to be 
Proved that nuclear instability, coming to be well recognized, is 
Connected with disturbed nutrition, and also whether a smaller 
or larger number of chromosomes necessarily determine a gamet- 
ophyte or a sporophyte. 
- cn whole, therefore, Professor Bower still maintains that 
phyte is the result of the gradual elaboration of the 
