Tlie Koj'äl iSeciofy, Loiidoii. 75 



spccies, piothalli, wliicli undor normal coiulitions -wonld have 

 produccd normal embryos, bccame, aftcr a lonf;(M' or shortor 

 period. apo^amoiis. Fnrther therc was a gcnoral similarity in tlie 

 clianges of form and structure of the prothallus, Avhicli preceded 

 this result. Tliis form of ai)og-amy, occurring aftcr prolonged 

 cultivation of normal protlialli ander special conditions, may be 

 distinguished as induced apogamy, in confradistinction to dircct 

 apogamy, by whicli is meant tlio immediato })roduction of vegetative 

 buds by protballi, which are usually incapablc of being fortiliscd. 

 Both forms occur in Kephrodhim FiUx-mas. 



The causes Avhicli appeared to induce apogamy in thcse 

 l)rotlialli wcre thc prevention of contaet witli fluid water which 

 rendered fertilisation impossible, and the cxposure to direct 

 sunlight. Possibly the thcmperature also had some effect. Thc 

 case of Kephrodium Filix- mas shows that the variable condition 

 of the sporo})hyte, as indicated by cresting, &c., though possibly 

 prodisposing to the ehanges w^hieh lead to apogamy, does not 

 stand in any necessary conneetion with the phenomenon. 



Shat different degrees of apogamy are distinguishable was 

 also shown by these cultures. The cylindrical process, arising 

 from the apex of the prothallus, or from its undcr surface, is to 

 1)0 regarded simply as a modiücation in form and structure of 

 the gametophyte de})endent on the altered conditions, and possibly 

 a direct adaptation to these. The next stage is seen in cylindrical 

 processes, which, while bearing sexual organs, also producc isolated 

 members of a sporophyte (roots, i-amenta, sporangia). It is to be 

 borne in mind, however, that tissue diffcring from the rest of the 

 process always occurred beneath the last-named structures. The 

 final stage is the production of a vegetative bud capable of further 

 growth as a typical sporophyte. In this a series Icading from 

 the bud cirising by transformation of the tip of a cylindrical 

 process, to liuds produced on or in the place of archcgonial 

 projections, and from this to buds situated on the under surface 

 of the prothallus itself can be recognised, 



The readiness with which the intermediate form between 

 gametophyte and sporophyte and the earl}'' stages of vegetative 

 buds reassume the prothalloid form, is worthy of note, as bearing 

 on some cases of apospory. 



These departures from the normal development of the pro- 

 thallus are not regarded as reversions in the ordinary sense, but 

 as indications of the capability of direct response to altered 

 conditions possessed by the gametophyte. Their possibe importance 

 in relation to the theory of homologons alternation appears to the 

 writer to bc of this nature. It that theory be true, the sporophyte 

 and gametophyte are modifications of a similar torjn. The 

 gametophyte, especially the simple free living prothallus of the 

 Ferns, has departed less widely from that form. Such an organism 

 as a Fern prothallus would therefore appear to be suitable for 

 experimontal work, in the hope that its behaviour under altered 

 conditions would afford hints as to the sort of ehanges which, in 



