210 
TOPULAR SCIENCE REVIEW. 
lamina or blade of tlie embryo leaf l, tlie two sides of which 
are folded together and which is bent downwards on its petiole. 
Behind is another stipular bud consisting of two stipules inclos- 
ing another inverted embryo leaf. Farther dissection reveals 
other embryo leaves on a constantly diminishing scale of archi- 
tecture, b, the linear mark on the shoot, or scar made by the 
stipular leaves, which are, in fact, only another variety of 
winter leaves. There are seven dots on the leaf-scar. 
These shoots were collected in autumn. The Liriodendron 
tulipifera, which is a deciduous-leaved tree, has still attached to 
its apex one of its leaves, which is purposely left there, hr 
order to give the reader a correct idea of its peculiar trun- 
cated form, and also a clear view of the embryo leaf b. 
The lower and less developed herbaceous plants have also a 
winter’s life and an appropriate shelter for that life, as well as 
the trees. The seeds of annuals and also the rhizomes, or under- 
ground stems of perennials, like the buds of trees, are only so 
many winter retreats into which the exhausted life of these 
plants retires for protection, repose, and recuperation during 
the winter months. “ Seeds and resting-spores,” says Hen- 
frey, “ are organized in a manner especially adapted to pre- 
serve their latent vitality from injury by external influences. 
They can withstand great variations of heat or cold, especially 
in the absence of moisture. Most seeds will bear a tempera- 
ture very far below the freezing-point if kept dry, and many 
will bear an exposure to 100° or 110°Fahr. in dry sand. 
Prolonged immersion in water at 120° kills most seeds unless 
the skin is very thick and they contain oil instead of starch in 
their endosperm.” 
The seeds of the Whitlow-grass ( Draba verna), of the 
different species of chickweed ( Gerastium and Stellaria ), of 
the fumitory and corn-cockle, are sown early, and are, there- 
fore, exposed to the excessive heats of summer as well as to 
the cold of winter, and yet they come up at then- appointed 
season. So carefully has Nature prepared the seeds of these 
plants for the vicissitudes to which they are exposed ! Draba 
verva , for example, is never scarce. This plant is quite 
common in Pennsylvania, as well as in England. There is 
no flower which has interested the writer more than this 
lowly annual. It is one of the least developed of all the 
Crucifer*, whether we consider its leaves, whose vegetative 
power is so enfeebled that they do not form a sufficient 
amount of stem to separate them from each other, but remain 
in a stellate cluster on the ground ; its tender capillary scape, 
or flower-stem, which only rises to a height of from one to 
three inches above the ground ; the two or three small white 
flowers which that scape supports ; or the brevity of its life, 
