Hollow ay. — Prothallus, <&c, of Tmesipteris. 419 



the very early adoption of the fungal habit by the young sporophyte and 

 its consequent ability to nourish itself. However, the dependence of the 

 young sporophyte upon its prothallus is a protracted one, and the absence 

 of the suspensor is compensated for by the development of haustorial 

 protuberances from the foot, just as is found, only there not to so great 

 an extent, in the sporogonium of the Anthoceroteae. The inference seems 

 to be that the superficial position of the embryo and the absence of the 

 suspensor is the more primitive condition. 



There are only two main body-organs in the embryo and young 

 sporophyte of Tmesipteris — namely, the shoot and the foot — there being 

 no trace of root, cotyledon, or suspensor. Thus its embryogeny is the 

 simplest among existing Pteridophytes. It would be difficult to conceive 

 of a more simple organization for a vascular cryptogam, and in instituting 

 comparisons we are forced to look to the young sporogonium of Anthoceros 

 rather than to any Pteridophyte embryo. While not suggesting that 

 Tmesipteris has been actually derived from the Anthoceros cycle of affinity, 

 it is clear that the absence from the former of any such organs as root or 

 cotyledon suggests that they approximate in so far as they both represent 

 primitive lines of development. In his Origin oj a Land Flora Bower 

 contemplates the fundamental structure -plan of the various pteridophytic 

 types of embryo as a spindle-shaped axis with the shoot-apex situated at 

 the apex of the epibasal region. The embryo is primarily a shoot, and 

 the other main body-organs are appendages developed secondarily upon 

 it. Speaking of the light which it was hoped the embryogeny of the 

 Psilotaceae would throw upon this matter, he says {ibid., p. 421), " If 

 the embryo develops without appendages directly into the rootless and 

 leafless rhizome, then either reduction has been effective back to the 

 earliest phases of the individual, or the sporophyte at first represents 

 that primitive state of an axis without appendages which a strobiloid 

 theory contemplates in the far-back ancestry." That the simplicity of 

 Tmesipteris is not due to reduction is a belief which has been greatly 

 strengthened by the discovery of the rootless and leafless Rhyniaceae. 

 The embryogeny of Tmesipteris as described in the present paper makes 

 more clear - cut the theory of the origin of the sporophyte of the 

 Pteridophyta from an Anthoceros-\ike sporogonium. 



Pursuing this theory further, it may be noted that two definite 

 suggestions based on the embryogeny of existing Pteridophytes have been 

 put forward as to how this origin could have taken place. Campbell 

 (2, p. 210) would see in the young embryo of Ophioglossum moluccanum a 

 primitive type of Ophioglossum which can be derived from an Anthoceros- 

 like ancestor. In this species the lower portion of the embryo forms the 

 large foot and the upper the cotyledon, the latter, however, not being 

 sporogcnous, as is the upper part of the sporogonium of Anthoceros. The 

 new organ in Ophioglossum is the root which arises at the junction of the 

 cotyledon and the foot. There is at first no stem-axis, this being developed 

 late as a secondary structure upon the primary root. Campbell links up 

 Ophioglossum, which he regards as " the most primitive type of the fern 

 series " (ibid., p. 42), with the Bryophytes in the suggestion that the 

 Anthoceroteae progressed to the formation of a root from the basal meristem 

 of the sporogonium, and that the " ^ro-Ophioglossum, " produced spores 

 upon the first leaf. Bower (1, p. 469) has criticized this theory by 

 pointing out that for his primitive form Campbell has chosen the most 

 abnormal of all the species of Ophioglossum, instead of starting with such 



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