10 A FLORA OF MANILA 
Cassytha, Loranthaceae, etc. Certain plants that grow on decaying organic 
matter and have no green tissue are called saprophytes. 
Plants that live but a short time, a few weeks or months, and die 
after producing flowers and seeds are called annual, like many herbs; 
those that live for two years, producing flowers and seeds the second year 
and then dying, are called biennial, but these, although common in tem- 
perate countries, are rare in the tropics; those that live from year to 
year, like all trees and shrubs and many herbaceous plants with under- 
ground stems, are called perennial. 
THE STEM.—The stem is the axis of the plant, to which are attached 
all other parts. In most plants the stems are very evident, but in some 
species: they are entirely underground. Plants that show no obvious 
stem above ground, but bear only leaves and flower-stalks, are called 
stemless or acaulescent. 
Stems above ground may be simple or branched. They are usually 
composed of nodes, the place on the stem or its branches where one or 
more leaves or branches are borne, and internodes, the spaces between 
the nodes. 
Special kinds of stems or branches have received distinctive names, 
such as culm, the hollow or solid stems of the grasses with well-defined 
nodes and internodes; sucker, a branch arising from the stem or from 
roots underground or from adventitious buds on the trunk or larger 
branches of shrubs or trees, the latter being called stem-suckers; and 
stolon, a branch from above ground that becomes prostrate and strikes 
root at the tip or nodes, producing new plants. 
As to differences in texture, stems are classified as herbaceous when 
living for a short period, forming no permanent woody tissue, and dying 
after flowering; suffrutescent when more or less woody or half-woody, at 
least at the base; and woody when forming permanent woody tissue 
lasting from year to year as in all shrubs and trees. 
As to direction, stems are erect when they. ascend perpendicularly 
from the base; ascending when rising obliquely; decumbent when more 
or less reclining on the ground at or near the base; prostrate when lying 
flat on the ground; creeping when closely appressed to the ground and 
rooting at the nodes; climbing or scandent when ascending by means of 
the support offered by other plants or objects, whether by tendrils, 
special spirally twisted organs, by rootlets, or by*other means. Vines 
that climb by coiling about other stems or objects are called twining. 
Underground stems assume various forms and are frequently con- 
founded with roots. There are four principal kinds, the rhizome or 
rootstock, the tuber, the corm, and the bulb. The rhizome or rootstock 
is a more or less modified creeping stem growing beneath the surface 
of the soil; the simpler forms are slender and consist of nodes and 
internodes bearing scales, as in the mint (yerba buena), various perennial 
grasses, etc., but other forms are thick and fleshy, as in the ginger (luya). 
A tuber is a stout, thickened portion of a rootstock, bearing buds (eyes) 
on the sides, as in the potato, but intergrades occur between this and the 
preceding. A corm is a short, thick, fleshy, underground stem, usually 
sending off numerous roots from the lower part, "and leaves and flowers- 
stalks from the upper, as in the taro (gabi). A bulb consists of a smail 
basal solid part, its bulk being made up of thickened scales; those in which 
the scales closely enwrap each other are called tunicated bulbs, as in the 
