(135) 
into bodies of various shapes. The plants vary greatly in 
size and structure and are both parasitic and saprophytic. 
To this group belong the yeasts and mildews. Some plants 
grow above the surface of the ground, as in the case of the 
morel; while others are subterranean, as in the case of 
truffles. Next in order are the alga-like fungi (case 32); 
these vary in form from simple masses of protoplasm to sim- 
ple or branching threads. Here belong many of the moulds 
and similar forms which grow both on other plants and on 
animals. The fifth and in many respects the most interesting 
of all the groups is that consisting of the lichens (cases 33 
to 36). The fungi thus far considered are either parasitic or 
saprophytic in their mode of life; the lichens form an indepen- 
dent symbiotic group, each lichen consisting of a fungus and 
an alga living together, the one nourishing the other. The 
lichens are quite familiar to most people as plants of more or 
less leathery texture growing on rocks, on poor soil or on 
the trunks of trees. 
A step forward brings us to the Bryophyta, or seedless 
plants with roots, stems and leaves, but without vascular tis- 
sue (cases 37 to 48). This group is best known through the 
mosses, which form its largest division; but of simpler struc- 
ture are the hepatics or scale-mosses (cases 37 to 40); al- 
though they were formerly associated with the true mosses, 
their tissues are much less differentiated than those of the 
mosses and the structure of their various organs much less 
complicated. The stems and leaves of the hepatic plant 
are sometimes combined into a flat thallus-like body which 
creeps closely on the ground or other objects and resembles 
in aspect some of the more simply organized plants. The 
leaves, too, are more like scales than in the true mosses and 
they do not have a midvein. ‘These differences alone enable 
one to distinguish a hepatic from its relatives by the unaided 
eye or at most by the use of a lens. In addition to these 
characters, the capsule or the receptacle which bears the 
spores, or reproductive bodies, usually splits into four valves 
when full-grown and the spores themselves are accompanied 
