80 CROCION ACHLYDOPHYLLUM 
The cells composing the periblem are parenchymatous with 
cellulose walls more or less polyhedral in outline and elongated 
vertically. In older specimens the cells become more or less irregu- 
lar in outline with intercellular spaces and contain few starch 
grains. The hypodermis is composed of a single layer of cells. 
These differ from the inner cortical layers of cells in having their 
cell walls thickened and more so on the lateral and external walls. 
(Fig. 6 Hy.) 
The epiblema is composed of a single layer of cells which are 
somewhat longer anticlinally. The cuticularisation is much more 
pronounced than in the cell walls of the hypodermis. The epiblema 
of more advanced primary roots shows quite an amount of cutin 
on the outer walls of the cells, where it gives rise to a layer of, 
more or less, equal thickness (cuticle) (Fig. 6-7 Ep.). 
THE Hypocotyy. (Fig. 8). 
The cross section of the hypocotyl (Fig. 8) was made a little 
below the petioles of the cotyledons. The intrastelar tissue although 
presenting no peculiarities different from those of the well advanced 
primary root, shows much greater secondary changes. As in 
primary roots, the protoleptome abutting on the endodermis is 
still visible though gradually diminishing in size due to the encroach- 
ment of the secondary leptome. ‘The proto-and metahadrome 
vessels are surrounded by secondary hadrome vessels of increasing 
caliber toward the cortex. ‘The secondary tracheae are mostly 
of the spiral and more rarely of the scalariform type. ‘The endo- 
dermis which is composed of very irregular cells is very distinct. 
The cortical parenchyma differs in no way from the cells of the 
periblem of the primary root as to structure but there is a noticeable 
increase in size of the cells of the former. Chloroplastids are con- 
fined chiefly to the layers of the cells exterior to and bordering 
upon the endodermis and intercellular spaces are scattered through- 
out the cortex. The cells of the epidermis show a marked cutini- 
zation on the lateral as well as outer and inner faces. 
COTYLEDONS. (Fvg. Q). 
The petioles of the cotyledons are somewhat flattened along 
their ventral and dorsal faces. The epidermis is composed of thick- 
walled cells in which they are anticlinally larger than periclinally. 
The ground substance is composed of thin-walled, many-sided, 
