346 
one light and shrivelled, which has given existence to the growing plant; 
the other solid and forming, destined for the support of a plant in the 
following year. I once met with an orchid which had been buried too 
deep by drift, and whose young tuber, as in the case of the tulip, was 
formed at the side of the stem instead of at its base. 
The effects of different depths of sowing on the germination of seeds 
was tested experimentally by Petri, who obtained the following results : 
Seeds sown to the depth of 
\ inch. 
1 inch. 
2 inches. 
3 inches. 
4 inches. 
5 inches. 
6 inches. 
Came above ground in 
11 days. 
12 days. 
18 days. 
20 days. 
21 days. 
22 days. 
23 days. 
No. of plants that came up 
7-8ths. 
All. 
7-8ths, 
G-8ths. 
4-8ths. 
3-8ths. 
1-8 th. 
When germination has proceeded so far that the cotyledons or the 
seminal leaves appear above ground the young plants are nourished by 
food obtained from the soil and from the air. A moderate quantity of 
the various materials required may enable a plant to grow in a healthy 
condition, to build up its structure, and to propagate the species by per¬ 
fecting seeds. But the object of the farmer is not to grow plants in a 
normal condition merely ; his object is, or ought to be, to obtain the 
greatest amount of vegetable produce in the shape of leaves, roots, seeds, 
or fruit, at the least expense of land and labor, and without exhausting 
or impoverishing his soil. In order to accomplish this, he must feed his 
plants ; to economise his food, it is desirable he should know what sub¬ 
stances are required by them, whether all require the same substances, 
in the same or in different proportions ; whether one substance is essen¬ 
tial to the healthy and vigorous development of one plant which is not 
required by another. 
He should know something of the origin of soils, what substances 
they naturally contain, and whence they are derived ; he should be ac¬ 
quainted with the composition of manures and the means employed to. 
increase their quantity and add to their value; he should know some* 
thing of the physical or mechanical character, as well as of the chemical; 
