THE EVOLUTION OF PLANTS 571 
accepted that the filamentous, alga-like fungi were de- 
rived from green alga:! 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. 1 
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." 2 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 519, Chapter XXXVIII. 
2 Scott, D. H. "The Evolution of Plants," p. 18. 
