Phyllotaxy

3724

Physical

Phyllotaxy, that branch of vegetable mor-
phology which discusses the modes in which
foliage leaves are arranged on the branches
of plants.

Phyllotaxy.
i. Opposite and decussate
leaves. 2. Alternate in five rows.
3. Alternate in two rows. 4. Dia-
gram of 'two-fifths' phyllotaxis.

Phylloxera (Greek phytton, 'a leaf/ and
zeros, 'dry'), a genus of insects belonging to
a family (Phylloxerinse) nearly related to
aphids and coccus insects, and included with-
in the suborder Homoptera in the order He-
miptera. The most important species is P.
vastatrix, which has wrought havoc among the
vineyards of Europe. It seems to have been
discovered in North America about 1854, and
in all likelihood was carried thence to Europe,
where it appeared about 1863.

Phylogeny, a biological term applied to the
ancestral history of a group of animals or
plants, in contradistinction to ontogeny, or the
development of the individual. See
OLOor; HEREDITY; EVOLUTION*

Phylum, or Phylon, in biology, the name

for one of the larger subdivisions of the plant
nd animal kingdoms. The former is usu:i!l\
divided into six phyla—Myxophyta, Schizo-
phyta, Thallophyta, Bryophyta, Pteridophyta,
and Spermatophyta. The animal kingdom is
usually divided into eight phyla—Protozoa,
Porifera, Ccelenterata, Vermes, Echinoderma-
ta, Anthropoda, Mollusca, and Vertebrata.

Physalis, a genus of herbaceous plants be-
longing to the order Solanaceae, They bear
violet, white, yellow, or purple flowers, the
calyxes of which become inflated during the
period of ripening of the fruit. This fruit, as
is the case of P. peruviana, the Cape Goose-
berry, and P. pubescens, is edible.

Physical Education. See Physical
Training.

Physical Geography. See Physiog-
raphy ; Geography.

Physical Society, American, an associa-
tion founded in 1899 for the advancement and
diffusion of the knowledge of physics: affiliat-
ed with the American Association for the Ad-
vancement of Science.

Physical Training, a branch of education
concerned chiefly with developing and train-
ing the body. The general aims of physical
training are, first, the promotion of health,
and, second, the formation of proper habits of
action. There are six distinct groups of exer-
cises used in physical training: they are free
movements of the arms, legs, neck, and trunk
(also known under the name of Calisthenics);
movements of the apparatus, such as the hori-
zontal bar, parallel bars, vaulting horse, buck,
rings, ladder, ropes, etc.; athletic exercises,
such as running, jumping, throwing weights,
etc.; combative exercises, such as boxing, fenc-
ing, and wrestling; games, such as baseball,
football, lawn tennis, golf, basketball, cricket,
lacrosse, etc.; and dancing, including various
forms, such as classical and folk dancing.
Every complete system of physical training in-
cludes exercises from all these groups. The
various forms of exercise are also classified on
the basis of their physiological effect on the
body. According to this classification there
are light exercises, such as free movements
with and without hand apparatus; exercises of
strength, such as lifting heavy dumb bells,
wrestling, etc,; exercises of speed, such as
short-distance running and swimming; exer-
cises of endurance, such as long-distance run-
ning and swimming; exercises of skill, such
as dancing and Indian club swinging, charac-
terized by complexity of movements and diffi-
culty of execution. The selection an4 the a.r-