252 BOTANICAL GAZETTE [APRIL 
students of biology, judging from the general neglect of the subject 
of polyembryony in the literature of organic evolution. Many o 
the important facts concerned in the process of embryonic selection. 
in gymnosperms, as the polyembryony of conifers and cycads, 
which have not been linked up with evolutionary doctrine, have 
been known to science for nearly a century. 
Besides being entirely inclosed within the tissues of the parent 
plant, developmental selection is characterized by being intraspe- 
cific or reflexive. It is always a definite competition between simi- 
lar individuals; usually it is between those of a single fraternity. 
3 
Struggle against unfavorable environment of 
hysical surroundings. 
pice debe ee Struggle against other species; extraspecific 
Environmental process oc- competition 
curring in external physical Struggle casi fellows; intraspecific competition. 
and biologi ae ee 
anism, where conditions of 
struggle for eitetics are very Selection between vegetatively branching parts of 
comptes either the gametophyte or sporophyte; buds 
and branches of trees, which later give rise to 
( reproductive parts. 
Interovular selection, between ovules within same 
ov t) after fertilization, largely due to 
vas UMN aula activities of contained embryos; (2) before 
Occurring during early fertilization, due in part to activities of con- 
Se tained female gametophytes, megaspores, or 
stages within tissues of 
parent plant, under condi- archesporial ells. : 
tions uniform for competing Embryonic selection, between embryos within the 
individuals same ovule, or within tissues of parent gameto- 
phyte. 
Gametophytic selection: (1) between male gameto- 
phytes, such as pollen tubes within carpellary 
and nucellar tissue; (2) between female 
gametophytes within the same ovule. 
Gametic selection: (1) between male gametes or 
‘ sperms; (2) between female gametes or eggs- 
Although it is realized that in many instances this developmental 
process is influenced by external conditions, it is clear at least that 
the influence of these environmental conditions is very indirect, 
and that the highly complex external environment does not exert 
