GLOSSARY one 
Phyllotaxis. Leaf-arrangement: alternate, or separate in 2, 
3, 5 or 8 ranks, on many plants; opposite,’or in groups 
of 2, in others; whorled, or in groups of more than 2, in 
still others. 
Physiology. The science of function in living things, classi- 
fying their parts as organs with respect to the work they 
perform. Organs of unlike morphological origin are anal- 
ogous to one another.—See metamorphosis; morphology. 
Pinna. One of the divisions of a pinnate leat. 
Pinnate. Like the plume of a feather: having the leaflets 
along a rachis, as applied to compound leaves (tamarind). 
Contrasted with digitate or palmate. 
Pinnule. A leaflet of a bipinnate or decompound leaf. 
Pistillate. Producing pistil, or seed-organ, but not stamens 
(ear of corn, “female” cottonwood). 
Pith. The central part of a dicotyledonous or exogenous 
stem, surrounded by the woody cylinder: usually continu- 
ous and of uniform texture, or gritty or surrounded by 
cells different from those at the center, or exceptionally 
with plates of firmer cells, or diaphragms, at the nodes 
(paper mulberry, grape) or at intervals between them 
(tupelo) though otherwise continuous; rather commonly 
_with cavities like a sponge (evonymus), or entirely exca- 
vated or disappearing, at least between the nodes (honey- 
suckle) so as to make the stem fistulous; not infrequently 
chambered between persistent thin plates or disks (wal- 
nut) when it is spoken of sometimes as discoid. 
Pithy. Sometimes used in the sense of having large pith 
and little wood. 
Pod. <A dry dehiscent seed-vessel. 
Pointed. The general equivalent of acute, acuminate or mu- 
cronate. 
Pollen. The male cells or microspores produced by flowers. 
Pome. An apple-fruit, with a papery or bony core at center 
and crowned by sepals or scars from which they have 
