LXIV OUTLINES OF BOTANY, 
, are termed cellular plants. Vessels have their sides very variously 
se some, called spiral vessels, have a spiral fibre coiled. up their 
when rs are i 
vessels is 8 
sine: they are of considerable a and visible to the naked eye in cross: 
sections of the stem, in othe 8 they are almost absent or can only be 
race stvatihitthor: 
89. modifications of the above peer are distinguished by 
Vepetihis 4 atiahaehtoks under names which need not be enumerated here 
8 not being in general practical use. Ai ited. pit turpentine-vessels, 
oul-reservoirs, etc., are sana cavities left between the cells, or large cells 
filled with peculiar secreti 
190. When tissues are once S toons d, they increase, not by the general 
enlargement of the whole of the cells already form ed, but by cell-division, 
that is, by the division of young and vitally active cells, om the en tr 
me ei i h mbr 
nc ie 
ion of the contents of a pre iously existing cell, the ‘erat sac, This 
is termed /ree adtfovindiion, i: in contradistinction ‘to cell-divi 
191. A young ay vitally active = — sts of the pan form 
les Pp ubst 
appea 
cell. As this cell increases e, and its walls i in thickness, the proto- 
plasm and watery cell- “sap che crs rbed or dried up, the firm cellu- 
os wall alone remaining as a permanent fabri c, either beeen 8 filled 
with various organized substances produced or secreted within 
192. The principal organized contents of cells ar re 
sap, the first product of the digestion of ope food of ean it con- 
tains the elements of vegetable growth in a dissolved con 
ich th 
sugar, of whic ere are two kinds, called can and grape 
sugar. It oma exists oe in the sap. It is wead pr Bene He in 
growing parts, in fruits, an n germinating see see 
extrine, or vegetable iii a gummy substance, between mucilage 
and starch, 
starch or fecula, one of the most universal and conspicuous of cell- 
contents, and often so abundant in fari rinaceous roots and seeds as to fill 
cell-ea i i 
Ww 
ines of growth. The chemical constitution of starch is the same as that 
of cellulose; it is unaffected by cold water, but forms a jelly with boiling 
water, an ‘turns blue when — by iodine. When fully dissolved it is 
no longer starch, but dex 
= whe hyll, — minute serikitilag: hg nitrogen, = coloured 
ler the on of sunlight. These granules are most abundant 
in the pean of cate immediately below the surface or schdoentes of ee 
