THE HAND-BOOK OE GARDENING. 
26 i 
ture then of clay and sand will be fertile without limestone, chalk, or 
basalt, that is, whinstone; and more particularly without decayed 
plants or manures, containing a large proportion of humic acid and 
other combinations of carbon and hydrogen. ” 
Changes of Plant Food.-— “When a soil is known to contain 
rotting weeds and other plants, or has had rotted manure spread over 
its surface, it cannot be too well dug and raked, in order to mix the 
richer parts of these with the less rich clay and sand; on the same 
principle that at dinner we mix in eating the richer beef or mutton, 
with the less rich potatoes, cabbage, and bread. Both we and the 
garden-plants must have a large portion of water to thin or dilute 
the food, otherwise health will suffer. The water which we drink in 
the form of tea, coffee, or beer, is similar in kind to the manured 
moisture sucked up by garden plants, which feed solely on liquid 
food.” 
The Sap and the Pulp. —“The change of sap into pulp cannot 
take place in the dark, sun-light being indispensable to open the 
pores; and hence plants growing under thick trees, or any thing 
that obstructs the sun’s light, cannot well effect this important 
change, and the pulp being in consequence only prepared in small 
quantity, they become slender, yellowish, and sickly, for want of due 
nourishment. It is ignorantly said, that the trees draw them. 
Plants in pots, in an ill-lighted window, suffer the same inconveni¬ 
ence, and bend their heads as much as possible towards the light; 
not that they have any knowledge of the use of it, any more than a 
hungry infant has of the use of the milk which it greedily sucks, 
but because, in the part most exposed to the light a greater quantity 
of pulp is formed, which renders it firmer, heavier, and shorter, than 
the part less exposed, whose laxness causes it to give way and 
lengthen, on the same principle that a piece of somewhat moist pa¬ 
per will bend when exposed to the heat of a fire, from the side near¬ 
est the fire losing its moisture and contracting.” 
“ When the change of sap into pulp is in any way prevented, as 
by shade or by moisture, the leaves naturally become yellow, as 
when plants in pots have more water given them in saucers or other¬ 
wise, than the sun-light can cause to pass off; or when they are root 
bound, and the root tips have not room to feed.” 
“ Bv tying the leaves of lettuce near the top, the inmost leaves 
are kept from the light, and hence little or no pulp being formed 
there, they are rendered white, crisp, and tender; as cabbages and 
savoys grow of their own accord without tying, though tying hastens 
the process. This is called blanching, which means “ whitening.” 
