l62 COOK 



Likewise, it is only in the capsules of mosses and of Antho- 

 ceros that we find a columnella or central pith of sterile cells 

 serving as a supporting axis. An internal framework is quite 

 as important as chlorophyllose external walls, if a capsule is to 

 be transformed into a vegetative structure. Ferns of the family 

 Hymenophyllaceag have their capsules clustered on the ends of 

 percurrent veins and surrounded by cup-like expansions of the 

 margins of the fronds, thus giving a striking superficial resem- 

 blance to the columellate capsules of mosses. But this appar- 

 ent columella of the Hymenophyllaceae bears many capsules, 

 instead of being enclosed in a capsule, as in the mosses and in 

 Anthoceros. Instead, therefore, of representing an ancestral 

 condition from which the fern phylum might have developed, 

 Anthoceros appears to be farther advanced than the ferns in the 

 direction of the angiosperms. 



The prothalli of ferns may be taken as the best indication of 

 the nature of their bryophyte ancestors. Fern prothalli viewed 

 as liverworts represent very primitive types. Their habit of 

 bearing archegonia on the under side may explain why a fern 

 sporangium, instead of developing merely a nursing-foot for 

 more efficient connection with its parent prothallus, found means 

 to get into communication with the ground. The development 

 of the capsule base of vegetative cells was then no longer lim- 

 ited by the supplies of water and nutrient substances which the 

 prothallus could provide, and the way w^as open for the evolu- 

 tion of a new plant structure. 



It is often assumed that the fern prothallus has degenerated, 

 since the sporophyte has so greatly surpassed it in size and 

 vegetative activity, but there is no very good reason for suppos- 

 ing that the prothallus is any smaller or less important now than 

 before. The theory of the reduced prothallus has been applied 

 to the ferns in order to reconcile us in advance to the assump- 



a narrow stalk with a small bulbous foot. In some species of Riclla the stalk 

 consists of a single row of cells, as in C. cavernarum, and the bulbous foot, 

 which in Riella is composed of more numerous cells, shows a tendency to form 

 absorbent processes. In all the Merchantiaceae and the Jungermanniaceae, with 

 these exceptions, the foot and seta of the mature capsule appear to be relatively 

 bulky. On the other hand, in the Ricciaceae the sporogonium shows no trace 

 of afoot." See Lang, William H., 1905. On the Morphology of Cyat/iodium, 

 Annals of Botany, Vol. 19, p. 424. 



