640 MOSSES AND FERNS 



one. He calls attention to certain resemblances in its anatomy 

 to that of Isoetes and believes that the latter and Phylloglossum are 

 related. 



P. 504. The gametophytes of both Psilotum and Tmesipteris have 

 recently been discovered (Lawson, i, 2). The gametophytes are 

 much alike, resembling in form that of Lycopodium Phlegmaria ; 

 but the sexual organs are much more like those of the Ferns. The 

 spermatozoids are multiciliate. Lawson is inclined to accept the 

 view that the Psilotaceae are related to the Sphenophyllales. 



P. 504. A study of the anatomy of P. flaccidum (Stiles (i) ) shows 

 a general agreement with P. triquetrum. In both species there is a 

 trace of secondary xylem in the stem-bundle. (See Boodle (6).) 



P. 506. It is likely that Tmesipteris is saprophytic rather than 

 parasitic. As in other humus-saprophytes, there is always associated 

 with the plant a mycorrhizal fungus, similar to that found in the 

 Ophioglossaceae, and the subterranean gametophyte of Lycopodium. 



P. 507. The literature on Tmesipteris has been carefully reviewed 

 by Miss Sykes (3), who also made a study of the structure of the 

 sporophyte. She considers the sporangiophore to be a branch having 

 two leaves, and terminated by a synangium composed of one or two 

 spongenous masses that have fused over the apex of the shoot. This 

 contradicts the view held by Bower. 



P. 510. For Bower (21), read (20). 



P. 510. Miss Sykes concludes that the evidence for associating 

 the Psilotales with either the Sphenophyllales or Lycopodiales is 

 inconclusive. ''They are better retained alone in the cohort Psilo- 

 tales." 



P. 518. There is a good deal of difference in different species as 

 to the time of development of the gametophyte within the macro- 

 spore. (See Bruchmann (8).) Thus, in S. spinulosa and S. Hel- 

 vetica the gametophyte is mostly developed after the spores are shed ; 

 while in S. rupestris the whole development of the gametophyte is 

 completed while the spores are still within the sporangium. Fertilisa- 

 tion may even occur while the spore is still within the sporangium 

 (e.g., S. apus), thus very closely approximating the condition found 

 in seed-bearing plants. 



Bruchmann also asserts that in some species the germination does 

 not begin until after the spores are shed. He gives no figures of 

 sections of the spores, so that it is not quite clear whether or not he 

 implies that the spore when shed had but a single nucleus. This 

 seems highly improbable. 



