424 
Development of Roots of Agricultural Plants. 
directed to the development of the plumule, or to the production 
of ramifications from itself with the same ultimate view. A 
constant interchange indeed is going on between the cells of the 
whole plant, so that no part is perfectly independent of the other. 
In the case of cereals, where the first rootlet which enters the 
soil has to force its way through the surrounding integuments, 
a very important supply is made through the scutellum, which 
remains in contact with the albumen till the whole of the nutri- 
tive matter is exhausted. 
So important, however, to the welfare of the plant is the acces- 
sion of new matter, which can be obtained only from the soil, 
even in the earliest stage of growth, that before any secondar}- 
rootlet is produced, the young radicle in many cases pushes out 
from its superficial cells a forest of delicate hairs, every one of 
which is employed actively in absorption. As far as I have 
seen, the radicle is at first perfectly smooth, as, for example, in 
the common onion ; but in general this condition does not con- 
tinue long ; and I have sketches of germinating seeds of several 
of the plants above mentioned, in which hairs were abundant 
shortly after germination. Sometimes these hairs do not appear 
at first upon the true radicle, but form a little coronet at its 
junction with the neck,* as in Iris sibirica. In some plants the 
connexion between the embryo and the seed is of very long con- 
tinuance, as in palms. The onion, however, affords a familiar 
example. The tip of the cotyledon is inclosed for a long time 
within the albumen, remaining bleached, and doubtless capable 
of absorption by its delicate surface. It will be observed, more- 
over, that if a speck of paint or ink is placed at the bend of the 
loop, which is made by the primary cotyledon on germination, 
the two parts increase in length, independently of each other, 
except so far as there may be an interchange of nutritious matter, 
the position of the speck remaining to the last unaltered. f 
It is clear from what is stated above, that it must be of great 
importance in the cultivation of cereals to have good sound seed. 
The first object is to ensure a quick and vigorous germination, 
which will scarcely be the case with thin, meagre seed derived 
from mildewed plants. No worse economy can be practised 
than that of saving a few shillings in the price of seed-corn. 
The germination will not only be comparatively slow, espe- 
cially in ungenial weather, but the weak plant will fall a sacri- 
fice to slugs and other vermin, if it does not assume, which 
* It is usual to call the •whole of the axis below the plumule " radicle ;" but there 
is often a marked difference between the true radicle and the portion of the axis 
from whence it is given oft', called by authors the neck or collum. Tliis is an im- 
portant matter in sugar-beet, as in that plant at least it contains little or no sugar. 
t This curious matter was first observed by Kichaid, who published a memoir 
on it in the Annals of the Museum of Natural History at I'aris 
