CRYPTOGAMS 297 
Beginning with the simplest forms, cryptogams are grouped 
in three great orders : — 
333. I. Thallophytes, or thallus plants.— This group takes 
its name from the thallus structure that characterizes its 
vegetation. In its typical form, a thallus is 
amore or less flat, expanded body, of which 
the lichens and liverworts offer familiar ex- 
amples among land plants, and the kelps and 
laminarias among seaweeds. It may be of gis 
any size and shape, however, and sometimes £2556 
consists of a mere filament, as in the com- $2993 
mon brook silk, or even of a single cell (Fig. Sz 
429). The term is applied in general to the 
simplest kinds of vegetable structure, in 
LS 
which there is no differentiation of tissues, Fic, 425.—Asea- 
and no true distinction of root, stem, and Weed with broad, ex- 
nded thallus. 
leaves. While it is not peculiar to the thal- soar os 
lophytes, it has attained its most typical development among 
them, and the name is therefore retained as distinctive of 
that group. It embraces two great divi- 
sions, the Alge and Fungi. The first 
includes seaweeds and the common fresh- 
water brook silks and pond scums, be- 
sides numerous microscopic forms whose 
presence escapes the eye altogether, or is 
made known only by the discolorations 
ge 2 and other changes caused by them in the 
eps water. To the fungi belong the mush- 
Fie. 426.—Anthoce- rooms and puffballs, the molds, rusts, 
ros, a liverwort with flat, mildews, and the vast tribe of micro- 
spreading thallus. . Z 7 a 
scopic organisms called bacteria, which 
are so active in the production of fermentation, putrefac- 
tion, and disease. 
334. II. Bryophytes, or moss plants. — This group likewise 
contains two main divisions, Mosses and Liverworts. Famil- 
iar examples of the latter are the flat, spreading green plants, 
