102 Instinct and Reason. [ February, 
fails to direct its stem, branches and leaves towards the sun; and 
in our typal plant, roots never fail to be thrust downward into the 
earth, in what form soever it may be placed in the ground. 
Leaves often change to roots, and roots in favorable circumstances 
become leaves. The greater the spread of foliage the more vig- 
orous and, consequently, the healthier will be the condition of the 
plant. At this point it may be well to note a universal law or 
principle: the more sunshine and air (of course at some time 
reaching a limit) the more abundant the foliage, and the denser 
the foliage the stronger and more flourishing the plant. This 
may be proved by comparing out-door plants with badly managed 
in-door and hot-house vegetation. Plenty of sunshine and air 
soon show a marked change for the better. 
Illustrating the subject by means of our type, we find the organs 
of a plant to be roots, leaves and the modifications of the leaves 
for reproductive purposes. The stem, or trunk, is but a canal, 
altering in size to suit the varying conditions of the plant, and is 
used for purposes of alimentation and the circulation of veg- 
etable products between the roots and the leaves. The growth 
of the stem depends upon the same law which governs the 
growth of the roots and the branches upon which the leaves are 
supported. In a word, the stem seems to act as a support for the 
leaves. Growth itself depends upon the proper assimilation of 
the elements of nutrition derived from the chemical changes 
occurring in the roots and leaves, and to some extent in the 
stem. 
Marine and fresh water alge, if deprived of roots, have 
in their remaining organs all the functions necessary for their 
peculiar mode of existence. 
The structure of a plant is cellular, showing its origin to be 
from the segmentation and accumulation of cells, one upon the 
other. The microscope shows how beautiful is the plant tissue, 
and how different in different varieties, but in every one this dis- 
tinct cellular formation is apparent. 
The plant is also possessed of the means for assisting its 
growth, as runners, creepers, tendrils and the like. For repro- 
ductive purposes it has nettles, thorns, elastic fibres, as in the 
seed vessels of the squirting cucumber (Momordica elaterium) ; 
but above all in its essential organs of reproduction—its flowers 
= containing the stamens and pollen, ovary and pistil. The first 
