108 EVOLUTION OF PLANTS 
conditions, as well as their abundance and variety, 
indicate a more modern type than the thallose forms 
with which they are connected by various intermediate 
conditions (Fig. 27, D). 
Some of the foliose Hepatice, especially certain tropi- 
cal types, show extremely curious modifications of the 
leaves to form reservoirs of moisture or even traps for 
small Crustacea, recalling those found in some flower- 
ing plants, such as the bladder-weed (Utricularia). 
The range of structure in the sporophyte of the He- 
patice is great, and a study of the different types is 
most instructive in showing the growing importance of 
the sporophyte in passing from the lower forms to those 
which approximate the structure of the higher plants. 
The simplest sporophyte is met with in the genus Ric- 
cia (Fig. 27, A, Fig. 28, B), which comprises a number 
of small thallose liverworts, where there is no trace 
of any differentiation of the gametophyte into stem 
and leaves; but the thallus is not so primitive as in 
certain other forms which have a more highly developed 
sporophyte. The sexual organs are borne upon the 
dorsal surface of the gametophyte, but not arranged 
in any definite order. They have the typical structure 
found in other Hepatice. The archegonium (Fig. 26, 
B) contains the egg in the enlarged ventral portion, 
and when the plants are covered with water, it opens 
and allows the spermatozoids, which have at the same 
time been liberated from the ripe antheridium, to swim 
into it. The spermatozoid penetrates the egg-cell, 
which thereupon is stimulated into active growth, and 
develops into the sporophyte, or sporogonium, as it is 
commonly termed in the mosses. The development of 
