44 VEGETABLE PHYSIOLOGY 
case of the zygote. In the Thallophytes this resting period 
is sometimes a long one; in the higher Cryptogams it is 
not so noticeable, and in the Phanerogams or Spermo- 
phytes, where the zygote is always developed inside the 
sporangium, it usually proceeds to active growth almost at 
once. In the latter plants, however, a resting period takes 
place later, after the seed is fully formed. The develop- 
ment of the young sporophyte, in fact, takes place in two 
stages, the one ending with what may be called the matura- 
tion of the seed, and the other beginning with the process 
of germination. Seeds when detached from the parent 
plant preserve their vitality for a variable length of time, 
sometimes even for years, and are capable of germinating 
freely when exposed to favourable conditions. 
The germination of the dicotyledonous seed occurs in 
one of two methods. In the first of these, the cotyledons, 
which are thick and fleshy, remain underground. When 
kept warm and moist the seed absorbs water and swells, 
the radicle makes its way out of the micropyle, the testa 
bursts, and the plumule makes its way upwards, the epi- 
cotyl, or part between the cotyledons and the first foliage 
leaf or leaves, circumnutating and emerging in the form 
of an arch, owing to the greater growth of one side. After 
reaching the air the growth changes, the greatest increase 
passing to the opposite side, so that the epicotyl straightens 
itself. During this time it subsists upon the nourishment 
stored in the cotyledons in the shape of reserve materials. 
We have already discussed the means whereby these 
digestive and nutritive changes are brought about, the 
agencies which effect them, and the various transformations 
which are met with. As the cotyledons remain under- 
ground this process is called hypogean germination. In 
the other method—that of the so-called epigean germina- 
tion—-the cotyledons sooner or Jater rise above the ground 
and become green, the hypocotyl behaving as does the 
epicotyl in the first case. These are frequently, though not 
always, albuminous seeds, in which the nutritive matter is 
