The Vegetalive Anatomy of Molinia caerulea. 53 
approached. The last of the extrastelar tissues, the endodermis, is 
of remarkable strength and prominence (Fig. 3, E): the cells in 
transverse section are as deep as they are broad, and each is the 
first of one of the radial rows of cortical cells; the outer wall is 
thin and straight; the inner wall is almost semi-circular, often 
thickened in the middle to three quarters of the depth of the entire 
cell, lignified, and pierced by a series of fine pits which apparently 
make provision for the transmission of solutions between the cortex 
and the vascular tissues within ; the middle lamellae are clearly 
defined especially on the inner walls. There are no cells in the 
endodermis which can be picked out by their structure as special 
passage cells : probably by virtue of the pits just described all the 
endoderinal cells are of that nature. 
neighbouring tissues. Lettering :—E, endodermis showing pits connecting 
with pericycle cells ; P, sclerenchymatous pith ; S, cortical storage tissue, 
inner zone ; V, large vessel; x, protoxylem ; p, protophloem, x 300. 
The stele (see Fig. 3) is enclosed in a pericycle of small, very 
thick walled, pitted cells, forming a ring made irregular by the 
convex surfaces of the endodermal cells to which they are applied. 
Within the pericycle we have the polyarch ring, usual in mono¬ 
cotyledons, of alternating phloem and xylem bundles, generally 
numbering from twelve to twenty-four pairs and usually some 
multiple of three. The phloem groups are relatively small. On 
the outside of them and adjacent to the pericycle is the protophloem 
(Fig. 3, p), the cells being smaller than the later developed elements 
and frequently compressed. The phloem consists of thin walled 
sieve tubes and companion cells arranged in groups of very irregular 
