Anthoceros laevis. 
509 
parenchymatous cells, which have fairly thin walls and con- 
tain chlorophyll, and probably these characters are of much 
greater importance than the position of the cells in relation to 
the archesporium. 
The conditions, to which these cells were exposed, must in 
the second place be considered. They were essentially similar 
to those under which the spores develop into the thallus 
(moisture, sufficient temperature, light), while like the spores 
these cells were more or less isolated from their neighbours. 
Under these circumstances they developed into the gameto- 
phyte. The most important factor in the environment of 
the young sporophyte, its position in and nourishment by the 
gametophyte, is entirely absent, and it is hardly too much to 
say that it would be surprising if under these circumstances 
the cells of a decaying sporophyte of a Liverwort or Moss 
produced sporogonia. The cases of apospory in Bryophytes 
appear to indicate the important influence of the environment 
in determining the origin of a gametophyte from an isolated 
cell of the sporogonium. All the sporogonia which have 
been experimented with were normal, and were obtained from 
wild plants ; there is here no question of a predisposition 
towards apospory such as complicates the problem in the 
case of some Ferns. The experimental conditions to which 
the cells have been submitted have brought into view certain 
of their properties which are not called into play in the 
normal life-history. 
The observations made on this case of apospory only serve 
to suggest the use of a thorough study of the conditions, 
to which the tissues experimented with are exposed, both as 
regards the inorganic environment and the alterations in their 
relations to neighbouring tissues. A knowledge of the facts 
regarding the influence of the change of environment, as well 
as those relating to the possible reconstitution of those cells of 
the sporophyte, which develop into the other generation, is the 
necessary preliminary to any estimate of the evidence afforded 
by apospory as to the nature of alternation of generations. 
Uutil further knowledge is obtained on these points it appears 
