NATURE STUDY. 
148 
more specialized but the less specialized forms give rise to 
higher forms in the evolutionary series. To illustrate from 
the history of the plant kingdom. This kingdom has 
been subdivided by different systematists. For present 
purposes it will be sufficiently correct to adopt the division 
into four sub-kingdoms, 1, Thallophytes, 2, Bryophytes, 
3, Pteridophytes, and 4, Spermaphytes. The first sub¬ 
kingdom includes Algae, Fichens and Phmgi; but since 
Fungi are, if in this order at all, de¬ 
graded plants, and Fichens are a 
combination (symbiosis) of Algae 
and Fungi, we may consider only 
the Algae. Of these there are four 
classes, Blue, Green, Red and 
Brown Algae. The Red and Brown 
Algae reached by far the highest 
degree of development as Algae and 
have undergone the greatest amount 
of specialization, so that they con¬ 
stitute the greater part of the known 
plants of their class. It was not 
from them, however, but from the 
comparatively insignificant Green 
Algae, that the primal members of 
the next sub-kingdom, that of the 
Bryophytes, were evolved. 
Next: the Bryophytes comprise 
Fig. 3. the Fiverworts and the Mosses. 
Today everyone knows what the Mosses are; great areas of 
the globe are clothed with them. But who, outside the 
limited circle of somewhat advanced botanists, knows three 
Fiverworts? Yet it is from them, and not from the enor¬ 
mously specialized Mosses, that the first fern-plant, the 
mysterious ancestor of Ophioglossum, was evolved. 
Next: the Pteridophytes comprise the Fern-Allies and 
