96  ErrerR: POLYEMBRYONY IN POLYPODIACEOUS FERNS 
than the other and would probably have been starved out by 
the larger one before it could have become independent of the 
gametophyte. 
Farnier (’92), while working out theembryogeny of Angiopteris 
evecta, observed and figured a prothallium bearing two young 
sporophytes, widely separated and perhaps located on two 
different archegonial cushions. 
Atkinson (’93) reported a case of “two independent plants 
from the same prothallium” in Adiantum cuneatum. 
In Botrychium Lunaria Bruchmann (’06) found that, in 
several prothallia examined, two embryos had started to de- 
velop, but in no instance were three found on one gametophyte. 
A number of large sporophytes and embryos were found by 
Lang (’14) in single Helminthostachys prothallia. Most of the 
embryos were small and aborted when found on prothallia with 
larger successful plants. He further observed that a number of 
archegonia must have been fecundated simultaneously in a few 
cases of prothallia which were attached to young sporophytes. 
Jeffrey (’98) during his work on Botrychium virginianum 
observed in one instance two sporophytes on a single prothallium. 
Campbell (’21, p. 147) found in Botrychium obliquum that 
one-celled embryos were common, as several archegonia may 
be fecundated and begin to form embryos, the inference being 
that two or more unicellular embryos were seen on a single 
prothallium. 
Czaja (’21, p. 565) succeeded in four out of six attempts in 
causing two embryos to develop on one prothallium of Gymno- 
gramme chrysophylla, and observed that both embryos of a 
single prothallium developed almost equally, but stated that 
these facts were not at all surprising since they were borne on 
old vigorous prothallia with large archegonial cushions. 
In a species of Aspidium, probably Aspidium Thelypteris, 
collected in its natural habitat, Buchholz (’22, f. 24) illustrates 
the occurrence of plural embryos. Two embryos were figured 
on a single prothallium, one of which had approximately 25-30 
cells; the other one was unicellular and was located about 1 mm, 
back of the sinus on the remote side of the archegonial cushion. 
He also illustrates (J.c., f. 25) what he believes to be a slightly 
later stage indicating the fate of the smaller embryo. The 
larger embryo (l.c., f. 25A) in this case had apparently attained 
