294 
Journal of Agricultural Research 
Vol. I, No. 4 
been variously called “hypocotyl,” “mesocotyl,” and “epicotyl.” By 
some it is held to be an intemode, by others merely an elongated node. 
The choice of a name for the organ depends on the interpretation of 
the homologies of the other parts of the embryo, particularly as to what 
is considered as constituting the cotyledon. If the sheath, or coleoptyle, 
be thought of as the cotyledon, the most appropriate name would be 
hypocotyl. Although this interpretation was accepted by Richard 
(1811), 1 Hofmeister (1858), and Sachs (1875), there seems to be little 
evidence in its favor and it is summarily dismissed by other mor¬ 
phologists. 
The two remaining views are as follows: 
(1) The scutellum alone is the cotyledon, the epiblast (absent in 
maize) representing a second leaf and the coleoptyle a third. The elon¬ 
gated axis between the coleoptyle 
and scutellum is thus considered an 
internode and is then given the name 
“ epicotyl.” Among the supporters 
of this hypothesis are the following: 
Warming (1879-80), Hackel (1887), 
Bruns (1892), Van Tieghem (1897), 
and Holm (1908-9). 
(2) All these organs, scutellum, 
epiblast, and coleoptyle, are viewed 
as parts of a more highly specialized 
cotyledon, in which case the term 
“mesocotyl” is applied to the portion 
between the coleoptyle and scutellum. 
With various modifications this last 
interpretation is adopted by Van 
Tieghem (1872), Hagelmaier (1874), 
Klebs (1881), Schlickum (1896), Celakovsky (1897), and Goebel (1905). 
Van Tieghem originally subscribed to the view that the coleoptyle was 
a part of the cotyledon, but as a result of further investigations aban¬ 
doned that position and adopted a modification of the views of Warming 
to the effect that the mesocotyl and coleoptyle represent a metamer dis¬ 
tinct from the scutellum. The epiblast he held to be a rudimentary 
second cotyledon. Van Tieghem carried this interpretation to its logical 
conclusion and adopted the view that the apparent similarity between 
the grasses and other monocotyledons did not represent homologies, but 
that the two groups were phylogenetically distinct. He further held, on 
the strength of anatomical differences, that the portion of the axis 
between the scutellum and the coleoptyle is in some grasses an internode 
and in others an enlongated node. The evidence regarding the mor¬ 
phology of the mesocotyl appears so conflicting that a definite interpreta- 
Fig. i.—D iagram of seedling maize plant, 
giving terminology of parts. 
1 For “literature cited” see p. 301. 
