42 
which have been made regarding the longevity of seeds 
have proved that so far a hundred years may be taken as 
the longest period for which seeds have been known to 
retain their power of germination. The seeds which enjoy 
such prolonged vitality belong to a restricted number of 
Natural Orders of which the Pea Family is one, remark- 
able like the others for the very resistant coat or testa with 
which its seeds are covered. : 
After the resting period, seeds when placed in favour- 
able conditions commence to germinate. Moisture and a 
warn. temperature favour germination. Water is absorbed 
by the seed coat as a whole, or may be taken in at certain 
points. In some small smooth seeds the outer layers of the 
seed coat are mucilaginous, and when wetted swell up 
considerably and become slimy. This is the case with 
the seeds of the flax plant (linseed) and with those of the 
cress. The probable reason for this special provision is to 
cause the seeds to become fixed in the soil so that the 
seed leaves can be more readily withdrawn from the seeds. 
There are generally present on the inside of the seed coat 
certain layers of cells which swell up rapidly when the 
seeds absorb water, and probably aid in the splitting of 
the seed coat, thus enabling the embryo to be gradually 
withdrawn from the seed. Warmth, the other factor 
essential to germination, is required for certain important 
chemical changes which need to take place before germina- 
tion can be effected. The food material stored in the seed 
is largely of a solid nature and requires to undergo trans- 
formation so that it can be dissolved in the cell-sap and 
can be conducted to the growing root tip and to the 
developing leaves. By certain fermentative changes starch 
is converted into sugar, oil and organic nitrogencus com- 
pounds are broken up and pass from cell to cell. In 
some cases as in peas and beans the food material is stored 
in the two fleshy seed-leaves or cotyledons, while in other 
seeds like those of the melon, the onion, and in all our 
cereals it is found in cells outside the young seedling and 
requires to be absorbed by the latter before it can be made 
use of at the growing points. The re-awakening of the 
vital processes indicated by these internal changes is 
marked by the commencement of respiration, that indis- 
pensable accompaniment of all life, whether animal or 
* Ewart, A. J. “On the Longevity of Seeds.” Proceedings of 
the Royal Society of Victoria, 1908. 
* 
