258 de Frciine . — The Morphology and Anatomy of the 
The hypocotyl, like the cotyledons, is red in colour and varies in length 
from 3 to 5 mm. It exhibits a marked contraction at the collet where 
it passes into the root. 
Occasionally tricotylous or even monocotylous seedlings are met with. 
The first pair of leaves are shorter and broader than the cotyledons 
and have very acute apices. It is not usually, however, until the second 
pair of foliage leaves is produced that, distinct excurrent veins arc de- 
veloped at the tips. 
The cotyledons have each a very small endarch collateral bundle 
throughout their main portion, but 
just at the base two very small lateral 
ones appear. The two main cotyle- 
donary strands enter the axis as en- 
darch collateral structures, the lateral 
strands also enter and those from 
the opposing cotyledons fuse, pass 
towards the centre of the axis, and 
sooner or later die out. The two 
cotyledonarystrands organize a diarch 
root according to van Tieghem’s 
Type 3, but no regular ‘ bifurcation’ 
and ‘ rotation 5 of the bundles occur, 
and the change from stem to root 
structure takes place in an ill-defined manner and very rapidly. 
Mucilage glands are numerous in the axils of the cotyledons, and 
Mettenius glands are also present on their surface. 
Root hairs occur, but are not numerous. 
2. The Root. 
The root system of S. binervosa usually varies in size more or less 
in proportion to that of the aerial organs. 
Thus the average height of plants taken from the crest of the 
laterals and the binervosa zone were respectively 22 cm. and 10-5 cm., 
the average rooting depths being 8-5 cm. and 4-5 cm. Tall plants of the 
Main bank had a rooting depth of from 18 to 26 cm. There is a main 
taproot which usually grows obliquely downwards. Large branches are 
few, but numerous fine laterals are developed which, like the main root, 
are characterized by their wire-like consistency. 
In the stele of the root of the young seedling the xylem occurs in 
the form of a diarch or triarch plate, with two or three alternating phloem 
groups. The pericycle consists of a single layer of thin walled cells, 
while the endodermis is well marked, with thickened inner and radial 
walls. The cortex is distinguished by its possession of a single ring of 
Text-fig. 8. Seedling plants of S. binervosa. 
x 2 . 
