118 BOTANY. 
to every part of the plant as it descends ; for the nourishment of the organs _ 
of a plant is supposed to be derived more from the sap that has been 
elaborated in the leaves than from the ascending sap in its original state. 
The rise of the sap in spring is one of the unexplained wonders of nature ; 
it cannot be ascribed to the mere increase of heat, for it begins in many 
plants during the very coldest weather of winter. They have had their 
period of rest, and their time of activity comes again. Plants need rest as 
well as animals. <A plant continually forced to grow, by artificial applica- 
tion of heat and moisture, soon ceases to live; and gardeners well know 
the necessity of allowing rest to hothouse plants. The plants of tropical 
countries often have their periods of rest and activity determined by the 
wet and dry seasons, which are to them as summer and winter. 
Reproductive Organs of Plants. 
The reproductive organs of plants are very different in the lower 
and the higher kinds. Of some of the lowest kinds we know nothing 
more than that they increase by the addition of one cell to another, 
and are propagated by the separation and diffusion of these cells; 
although it is probable that even these plants produce seeds or spores, 
by which they are multiplied. Their very minute size, however, makes 
it difficult to investigate the processes of their life. In- the highest 
kinds of plants, the reproductive organs are the flowers, and the fruit 
produced by them. | 
Flowers—Inflorescence.—The arrangement of the flowers upon a stem or 
branch is called the inflorescence! of a plant. In some plants, each flower 
arises from the root on a separate stalk; in others, it arises in like manner 
from the stem or from a branch. In some, many flowers are produced on 
a single stalk, and the upper part of a stem or branch often becomes itself 
a flower-stalk, its leaves becoming modified into bracts,* which are placed 
under each flower or each division of the flower-stalk. Bracts sometimes 
resemble the ordinary leaves of the plant, but are very often much smaller 
and less divided, and are sometimes membraneous and dry, sometimes of 
colours very different from the leaves. In some plants, the bracts are 
large, and in the bud enclose a stalk which produces numerous flowers. 
The bract in this case is called a spathe,? and the flower-stalk a spadiz.? An 
example is seen in the wake-robin, and palms have this form of inflo- 
rescence. In some palms, the spathe is very large, thick, and leathery, so 
that it is often made into a sack or bag; and there are palms which have 
a spadix twenty feet long, and bearing more than 200,000 flowers. 

1 From Latin in; upon, and floresco, to flower. 
2 From Latin bractea, a thin plate of metal, gold-leaf, 
3 From Latin spatha, a broad leaf, 
