White Pine.

SUB-KINGDOM I.

PROTOPHYTES.

The name Protophytes (_Protophyta_) has been applied to a large number
of simple plants, which differ a good deal among themselves. Some of
them differ strikingly from the higher plants, and resemble so
remarkably certain low forms of animal life as to be quite
indistinguishable from them, at least in certain stages. Indeed, there
are certain forms that are quite as much animal as vegetable in their
attributes, and must be regarded as connecting the two kingdoms. Such
forms are the slime moulds (Fig. 5), _Euglena_ (Fig. 9), _Volvox_
(Fig. 10), and others.

[Illustration: FIG. 5.--_A_, a portion of a slime mould growing on a
bit of rotten wood, x 3. _B_, outline of a part of the same, x 25.
_C_, a small portion showing the densely granular character of the
protoplasm, x 150. _D_, a group of spore cases of a slime mould
(_Trichia_), of about the natural size. _E_, two spore cases, x 5. The
one at the right has begun to open. _F_, a thread (capillitium) and
spores of _Trichia_, x 50. _G_, spores. _H_, end of the thread, x 300.
_I_, zooespores of _Trichia_, x 300. i, ciliated form; ii, amoeboid
forms. _n_, nucleus. _v_, contractile vacuole. _J_, _K_, sporangia of
two common slime moulds. _J_, _Stemonitis_, x 2. _K_, _Arcyria_, x 4.]

Other protophytes, while evidently enough of vegetable nature, are
nevertheless very different in some respects from the higher plants.

The protophytes may be divided into three classes: I. The slime moulds
(_Myxomycetes_); II. The Schizophytes; III. The green monads
(_Volvocineae_).

CLASS I.--THE SLIME MOULDS.

These curious organisms are among the most puzzling forms with which
the botanist has to do, as they are so much like some of the lowest
forms of animal life as to be scarcely distinguishable from them, and
indeed they are sometimes regarded as animals rather than plants. At
certain stages they consist of naked masses of protoplasm of very
considerable size, not infrequently several centimetres in diameter.
These are met with on decaying logs in damp woods, on rotting leaves,
and other decaying vegetable matter. The commonest ones are bright
yellow or whitish, and form soft, slimy coverings over the substratum
(Fig. 5, _A_), penetrating into its crevices and showing sensitiveness
toward light. The plasmodium, as the mass of protoplasm is called, may
be made to creep upon a slide in the following way: A tumbler