TRANSACTIONS OF SECTION D. 695 



I do not afBrm that the epidermic duct of Oivenia really represents the 

 segmental duct at an early stage of its phylogenetic development. I rather 

 think that we have here a case of homoplasy, not of homogeny. But I believe 

 that the homology of the primitive ureter is not a settled question, as the 

 American professor would have it, but that it remains a question open to further 

 investigation. 



Department of Botany. 



The following Papers were read : — 



1. On the Origin of the Sexual Organs of the Pteridophytes. 

 By Professor Douglas H. Campbell. 



While the close affinity of the Bryophytes and PteridopTiytes has been long 

 recognised in the origin and early divisions of the sexual org:ans, there exist 

 differences that have been looked upon as radical. This is especially noticeable in 

 the archegonium. 



A comparison of the structure and development of the sexual organs of the 

 higher hepatics (Anthocerotije) with those of the Eusporangiate Pteridophytes, 

 i.e., Opbioglosaefe, MarattiaceiB, Equisetinete, and Lycopodinese, shows remarkable 

 points of resemblance, enough to warrant the hypothesis that here is to be sought 

 the connection between the Bryophytes and Pteridophytes. 



2. Notes upon the Germination of the Sjyores of the Ophioglossece. 

 By Professor Douglas H. Campbell. 



Tfie gametophytic stage of these plants is very imperfectly known, and hitherto 

 only the very advanced conditions in two species. 



The author succeeded in germinating two other species — Ophioglossum (Ophto- 

 derma) pendidwn and Botrychium virginicum. In both the iirst division of the 

 spore occurs before any chlorophyll is formed. 



The author also found old prothallia of B. virginicum with young plants 

 attached, but too far advanced to study the development of the reproductive 

 organs and embryo. 



3. On Sterilisation and a Theory of the Strohilus. 

 By Professor P. O. Bower, F.R.S. 



In submitting a theory of the strcibilus to Section D it is assumed that 

 Hofmeister's general conclusions will be accepted, that antithetic alternation 

 was constant throughout the evolution of archegoniate plants, and that the 

 sporopbyte has been the result of elaboration of the zygote. The main points of 

 the theory may be briefly stated as follows : — - 



1. Spore-production was the first office of the sporophyte : its spore-bearing 

 parts are to be regarded as primary, its vegetative parts as secondary in point of 

 evolutionary history. 



2. Other things being equal, increase in number of carpospores is an ad- 

 vantage. A climax of numerical spore-production was attained in homosporoua 

 vascular cryptogams. 



3. Sterilisation of potential sporogenous tissue has been and is a widespread 

 phenomenon, appearing as a natural consequence of increased spore-production. 



4. Parts of the sterile tissue appeared as septa, partitioning off the remaining 

 sporogenous tissue into separate loculi. 



6. Septation to form synangia and subsequent separation of the sporangia aie 

 phenomena illustrated in the upward development of vascular plants. 



