882 : CONDITIONS OF. GERMINATION. 
GERMINATION.—By germination we mean that power or act by 
which the latent vitality of the embryo is brought into activity, 
and it becomes an independent plant capable of supporting 
itself. The germination of Cryptogams has already been suffi- 
ciently alluded to when treating of the Root, at page 135, and 
in the sections devoted to the Reproductive Organs, and Repro- 
duction of the Cryptogamia. Our further remarks will apply 
therefore solely to the Phanerogamia. 
Length of Time required for Germination.—The time required 
for germination varies much according to the nature of the seeds 
and the conditions under which they are placed. Generally 
speaking, seeds germinate most rapidly directly after being 
gathered. If preserved till they are quite dry, the process of 
germination in some cases is months in being effected, while in 
some seeds their capability of germination is entirely destroyed. 
The seeds of the garden Cress will frequently germinate in 
twenty-four hours, but the majority of seeds do not germinate 
for from six to twenty days, and some require months or even 
years. Germination is generally prolonged when the embryo is 
invested by hardened integuments or albumen, and it,is usually 
most rapid in exalbuminous seeds, more especially if such seeds 
bave thin soft integuments. Heat is the agent which most 
accelerates germination. : 
Conditions requisite for Germination.—A certain amount of 
heat and moisture, and a free communication with atmospheric 
air, are in all cases necessary to the process of germination. 
Electricity is also considered by some observers to promote it, 
but its influence in the process is by no means proved, and if 
exerted it is apparently of but little importance. Light has no 
influence on germination in most cases, according to Hoffmann’s 
experiments. (See also The Effect of the Electric Light on the 
Growth of Plants, page 858. ) e 
Moisture is required to soften the parts of the seed and to 
take up all soluble matters ; the cells of which seeds are com- 
posed are in this way enabled to expand, and the embryo to 
burst through the integuments, but excess of water is often 
injurious. 
Heat is necessary to excite the dormant vitality of the em- 
bryo, but the amount required varies very much in different 
seeds, and probably each species has its own proper range in this 
respect. Asa general rule, from 50° to 80° Fahr. may be re- 
garded as most favourable to germination in temperate climates, 
but some seeds will germinate at a temperature of 35° Fahr. ; 
and those of many tropical plants require a temperature of from 
90° to 120° Fahr., or sometimes higher, for germination. 
Air, or at least oxygen gas, is required to combine with the 
superfluous carbon of the seed, which is thus evolved as carbon 
dioxide, with a sensible increase of temperature (page 856), as is 
well seen in the malting of Barley. The necessity of a proper 
