_ ever, as laticiferous and vesicular vessels and glands, as wellas 
Sore called glandular hairs (Fig.92). : 
consists commonly of thin-walled succulent parenchyma 
~ manent cells. Groups are thus formed of particular kinds 
of cells which, united into strings or bundles, penetrate the 
“the fort a a meta or igine on the apex of SE cells, they 3 
The primary cortex which developes out of the serblene De 
containing starch or chlorophyll ; other forms of cells, how- 
intercellular passages containing sap, may also occur in it. 
: ‘In some plants masses of cork are found deeply buriedinthe 
~ cortical tissue, or even beneath it, the outer parts then dying, "4 
and falling off in the form ‘of bark, as occurs in the grape- 
~ vine and plane (see Figs. 66, 67, pp. 44, 45). ue 3 
Every mass of procambium consists, in its earliest stage, 
of similar thin-walled usually prosenchymatous cells, united 
together without any intercellular spaces. As the mass in- 
creases in age, some of the rows ofcells become transformed 
into vascular or bast-cells, and from these as centres the 
transformation advances of the procambium-cells into per- | 
rest of the tissue, and as a rule constitute a firm framework, Se, 
GA 
and form the jilrovascular bundles, or conducting bundles. 
-These bundles often lie isolated in the fundamental tissue 
continual formation of the tissue of which they are composed, 
that they finally almost entirely replace the intermediate 
- fundamental tissue, and form almost the whole of the sub- Re 
stance of the plant, as is the case in the wood of Dicotyle 
dons and Conifers. The transformation of the procambial 
so changed, or an inner layer of the procambium remains as 
‘the fibrovascular bundles either contain cambium or are 
_ destitute of it; the former being called ofen, the latter 
- closed bundles. In the open bundles the cambium is con- “ a 
of the plant, as for instance in the veins of the leaves; but 
they are generally socrowded and so strongly developed bythe 
cells into permanent cells either continues until they are all 
the formative cambiwm. As they become older, therefore, 
tinually forming new layers of permanent cells, and the part 
7 
