572 STRUCTURE AND LIFE HISTORIES 
TABLE V. SEQUENCE OF PLANT GROUPS, BASED ON THE 
MORPHOLOGY OF LIVING FORMS 
Thallophytes J Algae having chlorophyll, 
(no archegonia) \ Fungi no chlorophyll. 
f Bryophytes no vascular system. 
Archegoniates j Pteridophytes ) 
(archegonia, but no seeds) ] Calamophytes \ vascular system. 
Lepidophytes J 
Spermatophytes 
(seeds) 
Gymnosperms no closed ovary. 
Angiosperms closed ovary (pistil). 
Monocotyledons one seed-leaf. 
Dicotyledons two seed-leaves. 
pteridophytes from bryophytes hypotheses which, from 
other trustworthy evidence, as stated above, now seem 
untenable. 
Again, the table suggests that Angiosperms were de- 
rived from Gymnosperms, and therefore appeared late 
in the history of plant life; but the study of fossil plants 
shows that they appeared in the geological past, and were 
dominant in the Tertiary period, as now. We are led, 
therefore, to proceed with caution in drawing inferences 
based only upon a comparative study of the structure of 
forms now living. 
494. Evidence from Life Histories. In the study of 
the life history (ontogeny) of any higher sporophyte, 
we find that vegetative (sterile) tissues develop first. 
On the basis of this fact it has been inferred that all repro- 
ductive organs (stamens, carpels, sporophylls) arose by 
a modification of vegetative organs. Other facts, how- 
ever, lead to the directly opposite conclusion. 
496. Evidence from Comparative Ontogeny. In 
Chapters XVI and XXIII attention is called to the 
