634 MOSSES AND FERNS 



Ophioglossales is probably in the neighbourhood of Helminthostachys, 

 whichy on the whole, most nearly resembles the Marattiales ; but it 

 is improbable that the solid synangium which characterises most of 

 the living Marattiaceae was derived from a group of distinct sporangia 

 like those of Botrychium or Helminthostachys; and it is more likely 

 that it originated from some structure more nearly resembling the 

 spike of Ophioglossum. 



Angiopteris is, with little question, the most specialised of the 

 Marattiales, and has apparently departed furthest from the ancestral 

 type; while, on the other hand, Kaulfussia is probably the most 

 primitive of the existing genera. 



On the whole, the Marattiales are nearer the Leptosporangiatae than 

 the Ophioglassales are, and it is likely that the Leptosporangiates are 

 derived directly from some ancient Fern-types, related to the living 

 Marattiales, but differing from any of the existing forms." 



CHAPTER IX 



P. 305. The number of species of the Eusporangiatae is much 

 larger than the figure given. Christensen (i) recognises 192 species 

 of Ophioglossaceae and Marattiaceae, but probably some of these 

 should be reduced. 



P. 306. For Luerssen (7), read (6). 



P. 308. A very careful study of Apogamy and Apospory has been 

 made by Farmer and Digby (12). It was shown that where gameto- 

 phytes arose by apospory, the nuclei contained approximately the same 

 chromosome number as the sporophytic tissues. In such cases, the 

 young sporophyte developed either as an apogamous bud or else arose 

 from an egg-cell which had not been fertilised. 



In cases where the gametophyte arises in the normal way, i.e.y 

 from the germination of a spore having half the chromosome-number 

 of the sporophyte tissues, the formation of an apogamous sporophyte 

 is preceded by a migration of nuclei from one cell to another with sub- 

 sequent fusions of the nuclei, so that in this way the cells of the apoga- 

 mous sporophyte receive the double chromosome-number. 



P. 311. Pilularia Americana shows traces of a terminal annulus 

 like that of the Schizaeaceae (see Campbell (26) ). 



P. 314. Mottier states that in Onoclea monoecious prothallia are 

 found occasionally, although dioecism is the rule (see Mottier (4) ). 



P. 326. The origin of the stele of the young axis needs further 

 investigation. It is not at all unlikely that in the Leptosporangiate 



