432 BOTANICAL GAZETTE [MAY 
A new impulse was given to the study of embryology when 
COULTER and CHAMBERLAIN began the revision of their Mor- 
phology of gymnosperms (15). Especially was the impulse felt 
among the cycads. Cycads were collected from the oriental and - 
occidental tropics, and all phases of their life history investigated. 
The dicotyledonous nature of the cycadean embryo was demon- 
strated for all of them, even that of Ceratozamia (12, 13), which had 
been reported as having a single cotyledon. But while these 
embryos were shown to be normally dicotyledonous, exceptions 
to dicotyledony were seen to be by no means rare. The case of 
Ceratozamia was proved to be the result of abortion; but in Micro- 
cycas a condition was found in which the cotyledons were fused to 
such an extent that the author of the investigation referred to the 
fused structure as a “sheath,” and expressed the suspicion that 
monocotyledony, even in angiosperms, might have arisen in both 
these ways: suppression, as in Ceratozamia, and fusion, as in Micro- 
cycas. COULTER and CHAMBERLAIN, in their chapter on evolu- 
tionary tendencies (15), seem to give credence to this suspicion by 
requesting Sister HELEN ANGELA to illustrate her views on the 
subject of the primitiveness of polycotyledony and the tendency 
to reduce the number of cotyledons. 
From the material at my disposal, I was able to procure embryos 
in two different stages of development. The younger one was 
found to consist of an enveloping sheath, still meristematic 
and with four distinct lobes at its apex. Each lobe has its own 
vascular strand, four separate strands arising from the four poles 
of the root. The lobes are approximately equal in size at this stage, 
but not absolutely so, as can be seen from fig. 2. At the base of 
the sheath is the region from which the stem tip will arise later; 
at this stage it is not meristematic. Figs. 1 and 2 of the plate are 
sketches of the exterior and interior of the embryo at this stage, 
and fig. 3 is a cross-section which illustrates the irregular growth 
in thickness of the sheath, the region which bears the vascular 
strands resisting the pressure from without and giving the ap 
pearance of lobes and a four-sided aperture. : 
The second embryo studied (fig. 4) is older than the one just 
described. The sheath now consists of two regions, a lower portion 
