218 Sargant and Arber .— The Comparative Morphology of 
ColchiciLm aatumnale , L., is an example of a hypogeal Monocotyledon 
in which the very well developed upper sheath is stiffened by branches from 
the cotyledonary bundles, and not by the bundles themselves. We have 
examined two seedlings of this species. The upper sheath is stiff, long, 
and sharply pointed. The lower sheath is cylindrical and of some length. 
The primary root is stout and long; cauline roots do not appear early. 
We have complete series of sections from both seedlings, beginning in 
the upper sheath, and passing downwards, through the insertion of the stalk 
and the lower sheath, to the junction of sheath and axis, and the formation 
of the primary root. The only anatomical difference between the two 
seedlings is that in one of them there are two distinct bundles in the stalk 
of the cotyledon, each surrounded by its own endodermis, and that in the 
other the two stalk-bundles are in contact, and surrounded by a common 
endodermis. In fact, they form a typical double bundle as they enter the 
sheath. This difference is not so great as it may seem, for the distinct 
bundles of the first seedling also form a double bundle when they enter the 
lower sheath. In both seedlings the stalk bundles turn into it at once, and 
retain their characteristic double appearance until they enter the axis. 
But as they turn, each gives off a slender branch to the upper sheath, and 
these branches divide again on their upward way. They all end blindly 
near the apex of the sheath which they serve to stiffen. 
Three plumular traces are found at the first node. They represent the 
midrib and two lateral traces from the first leaf. The double bundle of the 
cotyledon is inserted on them, but it does not affect the symmetry of 
the triarch root-stele. The transition to root structure is extremely rapid, 
and the plumular phloem groups retain their position throughout. 
General Conclusions from Part II. 
In the introduction to this Part (pp. 206-8) we considered how far the 
evidence given in Part I could be used to support our interpretation of 
the Grass embryo and seedling. That interpretation has been outlined 
at the beginning of this memoir (pp. 164-9). It is illustrated there by the 
construction of an imaginary type X, linking the A vena type, which we 
consider as the most primitive of the three distinguished by Van Tieghem 
in the Gramineae, with the seedling skeleton of a real hypogeal Mono¬ 
cotyledon, Elettaria. 
The evidence given in Part I refers to the structure of Grass seedlings 
only. In discussing it, we have tried to show that all Van Tieghem’s types 
could be derived from the imaginary skeleton X } without any unprecedented 
or even improbable changes in structure. In Part II we have described 
seedlings from other families, whose vascular structure approaches that of X, 
and this evidence, too, must be summed up. 
