Embryo and of that of the Grass in particular . 51 1 
the bud. It cannot therefore be regarded as an independent phyllome, for 
its main portion on the posterior side, judging by the plastic processes of 
its construction, arises, not from a shoot, but from an older leaf. 5 That is 
to say, the coleoptile clearly arises, in the early stages of the ontogeny, 
as part and parcel of the scutellum. This is illustrated by Fig. 3 (a-e), 
taken from Celakovsky’s paper, and whose description of which I here quote. 
A shows the earliest stage in which the ligular outgrowth (here directed 
downwards) and the scutellum are clearly parts of one organ. ‘ In B the 
ligule is more developed and the angle between it and the scutellum has 
deepened, a is further separated from c, and the angle a b c is more obtuse 
than in A. In C abc has become very obtuse, so that the ligule is only 
slightly connected with the scutellum. In D the growth occurring towards 
the plumule has caused b to fall into the line a c , whereby all connexion 
between the scutellum and the ligular sheath is lost. In E, owing to the 
continued extension in the hypocotyl or in the cotyledonary node, a has 
Fig. 3. a-e, Grass-cotyledon, showing successive developmental stages, a c = limit between 
cotyledon and hypocotyl; a, the angle made by cotyledonary sheath with plumule; b , the angle 
separating the ligular outgrowth from the scutellum in A, B. (From Celakovsky after Hanstein.) 
become carried farther from b and c in the same direction, i. e. the base of 
the sheath becomes stretched along with the node, giving rise to the 
mesocotyl ( ab ). 
‘ As a result of all these processes, the limit between leaf and axis 
continually changes. The cell-tissue, which in A-C is included in the 
dotted triangle, there occurs above the insertion of, and belongs to, the 
cotyledon ; in D the same tissue, increased in amount by growth, has come 
to form part of the hypocotyledonary node, and when a mesocotyl is formed 
and elongates, the outer basal tissue of the sheath forms part of the meso- 
cotyl and constitutes the outer foliar-base of the sheath.' It is thus seen 
how the sheath and the scutellum (lamina of cotyledon) become separated 
from one another so widely, losing every trace of connexion. 
Hegelmaier also concluded, from his study of the development of 
Triticum vulgare , that scutellum and coleoptile together constitute the 
cotyledon. 
Great importance may be attached to these developmental data of 
the embryo. It is to them we should turn for light on the morphology 
