THE EVOLUTION OF PLANTS 571 



accepted that the filamentous, alga-like fungi were de- 

 rived from green algae by retrograde evolution (degenera- 

 tion). Were the plants with one seed-leaf (monocoty- 

 ledons) derived from those with two (dicotyledons) by 

 retrograde evolution, or were the dicotyledons derived 

 from the monocotyledons by progressive evolution? Evi- 

 dence, recently ascertained by studies of structure and 

 development, points to the conclusion, that, although 

 monocotyledony seems the simpler, more primitive con- 

 dition, it is really a later phenomenon, the monocotyledons 

 being derived from the dictoyledons by simplification. ^ 

 Again, a careful student of fossil plants has recently been 

 led to state that, ''it is beginning to appear more probable 

 that the Higher Cryptogams (ferns and fern allies) are a 

 more ancient and primitive group than the Bryophytes, 

 which would seem to owe 'their origin to reduction from 

 some higher type."^ In view of this diversity of opinion, 

 we learn at once that great caution must be used in in- 

 terpreting the evidence— that we must not ''jump at 

 conclusions." 



493. Results of the Method of Comparative Anatomy. 

 — By their study of comparative anatomy and morphol- 

 ogy, botanists have been led to propose the following 

 arrangement of plant groups as representing the general 

 course of their evolution (Table V) : 



From what has already been said, however, it should 

 be understood that such a table represents, not the line 

 of evolutionary advance, but the paths travelled by plants 

 in the course of their development. For example, it implies 

 that dicotyledons were derived from monocotyledons, 



1 See paragraph 522, Chapter XXXVIII. 



2 Scott, D. H. "The Evolution of Plants," p. 18. 



