1914] COULTER & LAND—MONOCOTYLEDONY 515 
case of the monocotyledonous embryos, the cells of one of the 
cotyledons gradually lose their meristematic activity, but those 
of the other one continue division, and as a result the so-called single 
cotyledon is developed, which is really the growth of the whole 
cotyledonary zone under the guidance of a single growing point. 
One cotyledon is not eliminated, but the whole growth is diverted 
into one cotyledon. Of course “tube”’ or ‘‘sheath” and ‘“cotyle- 
don” are all one structure, arising from the cotyledonary zone. 
As a result of the checked growth of one of the cotyledonary pri- 
mordia, there soon develops the appearance of an ‘‘open sheath” 
and a “‘terminal” cotyledon. The developmental stages in this 
case, therefore, are first two cotyledons, and then, because of one- 
sided growth, one large cotyledon and one so small as to be easily 
overlooked. ; 
The two primordia appearing upon the cotyledonary zone mark 
the places where vascular strands will be laid down. It would 
seem that the positions of vascular strands in such a case, therefore, 
are of no significance beyond indicating possibly the places where 
primordia have appeared, and also sometimes suggesting the num- 
ber of primordia; but they cannot be used even for these purposes 
with absolute certainty. 
It would be interesting to assemble the many cases of unequal 
cotyledons and note the variation in the checked growth of one of 
them, so that it ranges in appearance from a mere protuberance or 
ligule-like appendage, to a fairly well developed, but smaller, cotyle- 
don. Such a series can be observed among the so-called pseudo- 
Monocotyledons. In such a series it would be noted also that if 
the checked growth of one of the cotyledons is very early, it will 
contain no vascular bundles, all the cotyledonary strands being 
laid down in the growing cotyledon. In many cases, as in Cyrtan- 
thus, as growth is diverted from one cotyledon to the other, the 
procambium strands are also diverted toward the larger and later 
functioning cotyledon, and finally the strands unite. This phe- 
nomenon of fusing strands has been interpreted as an evidence of 
the fusion of cotyledons. In Fourcroya Bedinghausii, however, 
we found that the procambium strands of the primordium which 
represents a second cotyledon do not drift across and unite with the 
