THE COURSE OF BIOLOGIC EVOLUTION. 3] 



This difference of degree is so great that it practically 

 amounts to a difference of type, and far back in early Carbon- 

 iferous time the new type had begun to appear, seemingly 

 along two independent lines, the one typified by the form 

 called Noeggerathia and leading to the modern Cycadacese, 

 the other by the form called Cordaites leading to the modern 

 Coniferae, which two great families rivaled each other for the 

 mastery of the vegetable world during Mesozoic times. 



Origin of Pluenogamy — Gyinnospenny. — It is, however, 

 doubtful whether this great advance in the direction of strength 

 and stability of trunk would have alone sufficed to give these 

 new types the victor}- in the struggle with the tree-ferns, ca- 

 lamites, and lepidophytes of that epoch. Correlated with it 

 was a still greater advance in the structure of their reproduc- 

 tive organs. The highest types of modern cryptogams only 

 occupy the stage called heterospory, i. e., the possession of two 

 kinds of spores, the microspore, or male, and the macrospore, 

 or female spore. That stage was reached by all the higher 

 types of Carboniferous cryptogams. But by a series of steps, 

 which recent researches have enabled us to trace in living 

 forms, the passage was made in that earl}- day from heterospo- 

 rous cryptogamy to true gymnospermy, and the barrier was 

 crossed which separates the cryptogam from the phanerogam. 

 The origin of true flowers, albeit they were minute, incon- 

 spicuous, and devoid of color, fragrance, or beauty, took place 

 at that ancient date. The}' were some such flowers as our 

 sago-palms and our pines and cedars have to-day. Many fruits 

 have been preserved for us in the coal measures and some of 

 them closely resemble those of the ginkgo or maiden-hair tree. 

 There are other strong proofs that the earliest Coniferae be- 

 longed to the yew tribe of the ginkgo type, a type which is 

 now nearby extinct, having but this single living representa- 



