BOTANISTS AND DARWINISM. 103 
by any birds. Of the flowering plants there then existed 
only the two lowest classes, the pines and palm ferns, 
with naked seeds, whose simple and insignificant blossoms 
scarcely deserve the name of flowers. 
The phylogeny of Ferns, and of the Gymnosperms which 
have developed out of them, has been made especially clear 
by the excellent investigations which Edward Strasburger 
published in 1872, on “The Coniferze and Gnetacez,” as 
also “On Azolla.” This thoughtful naturalist and Charles 
Martins, of Montpellier, are among the few botanists who 
have thoroughly understood the fundamental value of the 
Theory of Descent, and the mechanical-causal connection 
between ontogeny and phylogeny. The majority of 
botanists do not even yet know the important difference 
between homology and analogy, between the morphological 
and physiological comparison of parts—which has long 
since been recognized in zoology—but Strasburger has 
employed this distinction and the principle of evolution in 
his “ Comparative Anatomy of the Gymnosperms,” in order 
to sketch the outlines of the blood relationship of this 
important group of plants. 
The class among Ferns which has developed most directly 
out of the Liverworts is the class of real Ferns, in the 
narrow sense of the word, the Frondose Ferns (Filices, or 
Phyllopterides, also called Pteridze). In the present flora of 
the temperate zones this class forms only a subordinate 
part, for it is in most cases represented only by low forms 
without trunks. But in the torrid zones, especially in the 
moist, steaming forests of tropical regions, this class presents 
us with the lofty palm-like fern trees. These beautiful tree- 
ferns of the present day, which form the chief ornament of 
