COMPOSITION OF VEGETABLES, 169 
624, Sir Humphry Davy, in his Elements of Agricultural 
mistry, has given an excellent account of the general 
‘composition of the various parts of vegetables. From this 
part of his work I have made the following extracts :— 
“ The tubes and hexagonal cells in the vascular system of 
plants are composed of woody fibre ; and when they are not 
filled with fluid matter they contain some of the solid mate- 
rials which formed a constituent part of the fluids belonging 
to them.” 
“ In the roots, trunk, and branches, the bark, alburnum, 
and heart-wood, the leaves and flowers; the great basis 
of the solid parts is woody fibre. It forms by far the 
greatest part of the heart-wood and bark; there is less in 
the alburnum, and still less in the leaves and flowers. The 
alburnum of the Birch contains so much sugar and mucilage, . 
that it is sometimes used in the north of Europe as a substi- 
tute for bread. The leaves of the Cabbage, Broccoli, and 
Seacale, contain much mucilage, a little saccharine matter, 
and a little albumen. From 1000 parts of the leaves of 
common Cabbage, I obtained 41 ae of mucilage, 24 of su- 
gar, and 8 of albuminous matter.” 
_ “Tn bulbous roots, and sometimes in common foul a 
large quantity of starch, albumen, and mucilage, are often 
found deposited in the vessels ; and they are most abundant 
after the sap has ceased to flow: and afford a nourishment 
for the early shoots made in spring. The potato is the bulb 
that contains the largest quantity of soluble matter in its 
vessels and cells ; and it is of most importance in its appli- 
eation as food. Potatoes in general afford from one-fifth to 
one-seventh of their weight of dry starch.” 
“The Turnip, Carrot, and Parsnip, afford principally 
saccharine, mucilaginous, and extractive matter. I obtain-_ 
ed from 1000 parts of common Turnip, 7 parts of mucilage, 
34 of saccharine matter, and nearly one part of albumen. 
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