1898-99.] Edith Chick on Eicinus Communis. 
665 
stages (shown in figs. 4, 5, and 6) are reached, the protoxylem 
now directed towards the centre is invested with this small celled 
tissue, which from its position is analogous to what Elot considers 
as perimedullary zone in the stem. It is interesting to note that 
these cells are continuous on the one hand with the pericycle 
below, and on the other with the perimedullary zone above. As 
the root is traced upwards to the “ collet, 55 the many layered peri- 
cycle is seen to get thinner, and by the time the “ collet 55 is reached 
the interfascicular pericycle consists of two, or at most three, layers 
of small cells inside the endodermis which now contains starch. 
On the other hand, the pericycle outside the phloem has not 
changed, and still consists of one or two layers of thin-walled cells 
external to the outermost point of the phloem arc, but is thicker 
on the flanks of the bundles. In somewhat older roots active cell 
division is to be seen in the pericycle marking the beginning of 
periderm formation. 
Hypocotyl. 
In the lower portion of the young unthickened hypocotyl ( i.e ., 
below the point of appearance of the foliar traces), the pericycle 
is visible between any two of the eight cotyledon bundles as a 
single layer of small cells immediately inside the starch sheath 
(fig. 27). 
In longitudinal section the pericycle cells are seen to be elon- 
gated, but with horizontal end walls, while the pith cells are much 
shorter and broader (fig. 28). In both transverse and longitudinal 
sections of an embryo the pericycle and pith presented exactly 
similar relations. When the interfascicular cambium arises, it is 
by tangential divisions in this layer of pericycle cells. 
The bulk of the £ primary ray 5 (in the old topographical sense) 
is occupied by a large celled tissue, on which the pericycle directly 
abuts, and which, following out Flot’s idea, we must regard simply 
as an outward extension of the internal conjunctive or pith 
(fig. 27). 
Opposite the bundle the pericycle is composed of tissue of two 
different kinds. Immediately beneath the endodermis is a layer 
of thin walled cells containing starch, similar to, and continuous 
with, the pericycle between the bundles; and between this and 
YOL. XXII. 2/12/99 2 U 
