446 Messrs Gardiner and Hill, The Histology 
lateral plumule, which is covered and protected by the cotyledonary 
sheath. After the primary root has attained some length the first 
leaf of the plumule commences to develope, and, pushing aside the 
lobes of the cotyledonary sheath, grows upwards with its tip sharply 
bent over (Fig. 4). The tips of the young leaves and the apex 
of the plumule are well provided with multicellular hairs, whose 
cells apparently contain oil. 
At about the same time the tissue just at the junction of the 
first leaf and the cotyledon divides and forms a small bulb or 
tuber, which is epicotyledonary in origin 1 (Fig. 5). As germination 
proceeds the reserve materials of the seed are gradually transported 
and re-stored as starch in the thin walled cells of the rapidly- 
enlarging tuber (Fig. 6). The primary root is replaced by adven- 
titious roots springing from the tuber, which by their shortening 
is pulled down deeper into the ground ; and finally the first leaf 
grows out into the air and develops a lamina not unlike that of 
the mature leaf of this plant (Fig. 7). 
A microscopical examination of sections of the ripe seed of 
Tamus shews that the hard brown testa consists of an outer layer 
of flattened cells, within which comes a second layer of deeply- 
pitted thick-walled cells, elongated in the tangential direction ; 
but in the vicinity of the micropyle this layer is more prominent, 
and the cells, which here are elongated in the radial direction, 
shew a larger number of pits than the corresponding cells in other 
parts of this layer. The little beak-like persistent micropyle is 
formed by cells of this character. Within this layer of thick- 
walled cells comes another single layer, which is succeeded by the 
thick- walled endosperm tissue (Fig. 3). 
The cells of the endosperm have thick and unpitted walls, and 
are arranged more or less radially with reference to the centre of 
the seed. They are filled with aleurone grains, oil, and some small 
crystals, which, together with the cellulose of the walls, form the 
chief reserve materials of the seed. No starch occurs in the ripe 
seed, but soon after germination has commenced a little may be 
seen in the cells around the embryo, just under the testa. If 
a section of the young germinatiug embryo is examined a large 
number of raphide-containing cells will be seen, which were not 
visible in the resting condition. These raphides, which apparently 
consist of Calcium oxalate, occur in the cortical tissue in special 
cells, which speedily become larger than those around them. 
The chief seat of deposition of these crystals is the upper portion 
of the cotyledon and the cotyledonary sheath. In older seedlings 
they are found in some abundance in the cortical tissues of the 
roots and leaf. As the depletion of the endosperm proceeds and 
the seedling increases in size the cotyledon enlarges considerably 
1 Cf. Bucherer, loc. cit., Le Maout and Decaisne, loc. cit. 
