512 Worsdell. — The Morphology of the Monocotyledonous 
SC-- 
of the parts concerned, and not to the later stages. In many Grasses 
the older condition is marked by the appearance, as above referred to, of 
the ‘mesocotyl’, i. e. an internode-like area becomes developed between 
the scutellum and the coleoptile. In some, e.g. Zizania , Leersia , 
Oryza , the mesocotyl is of very considerable length, and gives the exact 
impression of an internode (Fig. 4). Mere appearances, however, must not 
mislead us in this case. The early developmental history clearly shows that 
the coleoptile is part of the cotyledon (scutellum). Van Tieghem’s anatomical 
researches showed that the mesocotyl was not an 
internode, but the first, abnormally extended node. 
Schlickum also, by the same method, concluded 
that the mesocotyl possesses hypocotyledonary 
structure (Fig. 5). Sandeen found that the very 
long mesocotyl of Panicum has the same structure 
as an adventitious root. It is only necessary to 
read the papers of the two first-named authors, 
containing a record of exact observations into the 
anatomical structure of the mesocotyl, in order to 
see that, whether it belong to the node or the 
hypocotyl, it cannot, in any case, belong to the 
epicotyledonary region. Celakovsky points out 
that inasmuch as the coleoptile is proved by the 
developmental history to be part of the scutellum, 
the mesocotyl must therefore represent a much- 
extended node. The anatomy supports this. There 
remain over no other valid reasons, save those 
resting on mere appearances, for regarding it in 
any other light. What has really occurred during 
the elongation of the node is that the base of 
the coleoptile has become congenitally concrescent 
therewith, the ‘ carrying-up 5 of the sheath being 
due to this fact, just as the ‘ carrying-up ’ of a bract 
on a peduncle is due to congenital fusion of its basal 
region with that organ. A perfectly analogous and 
parallel case to the mesocotyl of the Grass-embryo 
is, as Celakovsky points out, to be seen in the 
axial extension which separates the leaf-stalk of 
Ficus elastica from its ochreate stipular sheath, and which is doubtless due 
to the same cause. 
Bruns’s arguments in support of the internodal character of the mesocotyl 
are easily refuted in the light of the known facts : his conclusions are based 
solely on the mere appearance presented by the mature embryo, without any 
reference to the important facts of the development. 
e---- 
Fig. 4. Zizania aquatica. 
Longitudinal section of em- 
bryo showing the scutellum 
{sc), epiblast ( e ), the elon- 
gated mesocotyl ( m ), and 
the coleoptile {cl). (After 
Bruns.) 
