EVOLUTION OF ANGIOSPERMS THROUGH APOSPORY l6l 



Finally, the growth of the capsule is persistent and indetermi- 

 nate. New tissue continues to form at the base and to push 

 up from below long after the terminal portion has ripened its 

 spores and shriveled away. 



A first step toward the derivation of angiosperms from An- 

 thoceros would be taken if the two-valved vegetative capsule 

 should acquire the power to pass through a resting stage and re- 

 new its growth, after the death of the parent thallus. Some of 

 the species of Anthoccros are perennial, even in very dry re- 

 gions, either by the survival of the tip of the thallus, or by 

 specialized tubers. The capsule continues to grow as long as 

 the thallus lives, and, as Campbell well says: '<A11 that is 

 needed to make the sporophyte entirely independent is a root 

 connecting it with the earth." Most of the liverworts, both 

 thallose and foliose, are able to survive long periods of drought, 

 as are also the moss "fruits" and the fern-fronds which corre- 

 spond to the capsule of Anthoceros. 



ANTHOCEROS NOT REPRESENTATIVE OF ANCESTRAL 

 PTERIDOPHYTE. 



It has been customary to utilize Anthoceros as the best living 

 analogy for an archetypal pteridophyte, but the sporangia or 

 capsules of ferns are much more similar to those of some of 

 the more primitive members of other orders of liverworts, such 

 as the Marchantiaceas and Ricciacese. It is only in the mosses 

 and in the Anthocerotaceee that the walls of the sporogonia or 

 capsules have become thickened and adapted to vegetative func- 

 tions. The fronds of ferns may be said to correspond to the 

 thickened capsule-bases of the Marchantiaceas and Jungerman- 

 niacese. The delicate stalked capsules themselves are still very 

 much in evidence in the ferns and have not assumed any vege- 

 tative functions.^ 



1 The diversity of liverwort capsules in these respects is shown by a recent 

 paper by Lang. 



" When we look for sporogonia resembling that of Cyathodium probably the 

 closest comparison as regards the relation between capsule and foot is presented 

 by SfhcBrocarpus and Riella. The mode of segmentation of the embryo in these 

 genera has much in common with the Marchantiaceae, the comparison between 

 Sphcerocarpus and C. cavernarum being particularly close. In both Riella and 

 Sphcerocarpus the mature sporogonium consists of a small capsule connected by 



