PLANT TISSUES 
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of the stomata by an accumulation of dust. They fill an important 
office in the dispersion of seeds and fruits, as with their aid such 
seeds as those of the milkweed and Apocynum are readily scattered 
by the wind. 
The reproductive organs of many Cryptogams are modified 
hairs, as the sporangia of Ferns. 
ENDODERMIS 
Endodermis is the “starch sheath” layer of cells, constituting 
the innermost layer of the cortex. In Angiospermous stems it 
usually resembles the other parenchyme layers of cortex as to struc- 
tural characteristics, save that it frequently contains more starch. 
In fern stems and roots of Angiosperms, however, its cells are clearly 
distinguished from the other cells of the primary cortex by their 
elongated form and suberized radial walls. In the roots of Mexican 
Sarsaparilla the inner as well as the radial walls are suberized; in 
those of the Honduras variety, inner, radial and outer walls all 
show suberization. Endodermal tissue is devoid of intercellular 
air spaces. Its cells contain protoplasm and nucleus. Its functions 
seem to be to give protection to the stele (tissues within it) and to 
reduce permeability between primary cortex and stele. 
CORK 
Cork or suberous tissue is composed of cells of tabular shape, 
whose walls possess suberized layers. Its cells are mostly filled 
with air containing a yellow or brownish substance. It is derived 
from the phellogen or cork cambium which cuts off cork cells 
outwardly. Cork tissue is devoid of intercellular-air-spaces. It 
forms a protective covering to the roots of secondary growth, stems 
(after the first season) of Dicotyledons and Gymnosperms, and 
wounds of stems and branches. Living cork cells contain protoplasm 
and cell sap while dead cork cells are filled with air. 
LATICIFEROUS TISSUE 
This form of tissue comprises either latex cells, laticiferous vessels, 
or secretory cells differing from each other in origin and method of 
development. Latex cells are elongated tubes which take their 
