BOTANY. 9 
the epidermis and its appendages being merely the general investment. 
The axis consists of a roof and a stem, growing generally in diametrically 
opposite directions. The axis is produced by the development of a spore, 
an embryo, or a leaf-bud, in two opposite directions. A spore is a young plant 
produced in the interior of another, without any agency of sexes, and 
having no determinate point of growth. An embryo is a young plant 
produced by the agency of sexes, and situated within a seed, having a 
determinate point or points of growth. <A Jleaf-bud is a young plant 
produced without the agency of sexes, inclosed within rudimentary leaves or 
scales, and developed on the outside of a stem. The spore and embryo 
propagate the species in the person of distinct individuals; the leaf-bud 
propagates the species in the form of an aggregation of individuals. When 
the vital action of either spore, embryo. or bud, is excited, development 
takes place upwards, downwards, and laterally or horizontally; im the first 
case causing an elongation of stem, in the second of root, in the third 
producing an increase in thickness. 
The root, or descending avis, is distinguished from the stem by the 
absence of normal buds and of stomata; in exogens there is generally no 
pith, although a medullary system is present. The objects of the root are 
twofold: to fix the plant firmly in the earth, and to absorb nutritious 
substances from the soil. Although roots are generally subterranean, they 
may sometimes be aerial. Such roots occur in epiphytes, or air plants, as 
also in species of Ficus, well shown in the Indian Banyan. In this case 
they are called adventitious, or abnormal. Green-colored aerial roots 
contain stomata. In certain parasites, as the Dodder or Cuscuta, roots are 
sometimes produced in the form of suckers, which enter the cellular tissue 
of the plant preyed upon. Roots exposed for a long time to the air, 
sometimes lose their fibrils and develope abnormal buds. 
The form of roots varies exceedingly with the manner in which the axis 
descends and branches. When this central axis goes deep into the ground, 
tapering towards the apex, and without dividing, a tap root is produced. 
When this tap root becomes somewhat shortened, and at the same time 
succulent, it constitutes the conical root, as in the carrot; when there is a 
slight rounding at both extremities, instead of a straight outline, the root is 
fusiform, as in the radish; when the axis is much shortened in proportion 
to the thickest diameter, we have the napiform root of the turnip; if the 
root end abruptly, as if bitten off, it is called premorse ; it may also be 
twisted. 
When the descending axis is very short, and at once divides into a 
number of nearly equal thin fibrils, the root is fibrows, as im many grasses ; 
when these fibrils are short and succulent, the root is fasciculated ; when 
the fasciculi are uniform and arranged like coral, the root is coralline ; 
when some of the fibrils are developed in the form of starchy tubercles, the 
root is tubercular ; it 1s nodulose when the fibrils enlarge in certain parts 
only ; moniliform when the enlargement is at regular intervals, and of 
nearly equal size, like a string of beads. The root may also be annalated, 
when divided by constrictions into partial rings; placentiform, when 
9 
