1922] BUCHHOLZ—VASCULAR PLANTS 265 
more than one sporophyte from a single gametophyte. This con- 
dition of polyembryony, which was casually mentioned by several 
students of pteridophytes, is well illustrated by fig. 24, which is 
a species of Aspidium, probably A. Thelypteris, collected in its 
natural habitat. While the larger embryo (fig. 24 A, e,) has 
become multicellular, having approximately 25-30 cells, the second 
one (fig. 24 B, e.), found on the remote side of the archegonial 
cushion, has remained unicellular, but has enlarged considerably. 
Fig: 25 is from a gametophyte collected on the benches of a 
greenhouse whose species could not be determined, but could have 
been one of a half-dozen leptosporangiate species growing near by. 
Fic. 24.—Embryonic selection in Aspidium: A, enlarged view of larger embryo 
of C, surrounded by calyptra; B, smaller unicellular embryo shown in C on same 
gametophyte, less than 1 mm. distant; (C reconstructed from several serial sections); 
A and BX 200, CX 42. 
This is included here because it seems to show a stage slightly 
later than that of fig. 24, and indicates the fate of the smaller 
embryo of the latter. It is especially interesting to note the 
shrunken and starved appearance of the embryo in fig. 25 B. That 
the larger embryo starves the smaller is a very natural explanation; 
this is a factor which is very certain to be involved, but it is also 
possible that the excretions of one embryo tend to inhibit the 
development of the others. In ferns having large vigorous gameto- 
phytes with many archegonia, if the aborted embryos are not too 
quickly starved they should be subject to recall experimentally, 
