482 OPHIOGLOSSALES 



development of spore-bearing parts as phenomena of reversion. This is 

 precisely the view which I take with regard to the fertile spikes of the 

 Ophioglossaceae ; the fact that when spore-production is suspended in 

 them a correlative vegetative growth may result, in form like that of the 

 sterile leaf, or some portion of it, is to be compared with the similar 

 cases of those ovules which are replaced by leaflets. In the case of the 

 Ophioglossaceous spike, as in that of the ovule, its replacement by a 

 body resembling a foliage leaf or leaflet does not demonstrate its 

 homology with, or its origin from, such a part : nor does the formation 

 of a lateral vegetative wing in place of the marginal sporangia, or 

 sporangiophores, show that the latter were in descent the result of trans- 

 formation of the former. 



There is also the inherent objection to Goebel's view, that it ascribes 

 the origin of the sporophyll to transformation of a vegetative leaf. It is 

 doubtless possible, by assuming a megaphyllous plant with elaborate 

 vegetative structure as pre-existent, to imagine its reduction and modifi- 

 cation to produce such forms of spore-bearing parts as we see in the 

 Ophioglossaceae. But to those who hold consistently to a theory of 

 antithetic alternation, with sterilisation as one of its most important 

 features, this assumption is not admissible : to them sporophylls are not 

 modified foliage leaves (compare Chapter XIII.). 



All the theories which would refer the spike in origin to some foliar 

 part, modified or altered, start from the more elaborate types of the 

 family, and assume reduction. But if the converse line be taken, quite 

 different views emerge. And there have not been wanting those who 

 have already approached the question of the morphology of the spike in 

 this way, which is certainly the most direct. 1 It seems more probable 

 that a sound view of the morphological nature of the spike should be 

 obtained through comparison of its simpler forms than of the more 

 complex with what is seen in other Pteridophytes : - and it is naturally 

 with the microphyllous forms that the closest correspondence may 

 accordingly be expected. 



1 Mettenius, Bot. Zeit., 1867, p. 98; Celakovsky, Pringh. Jahrbs., 1884, p. 291. 



2 An interesting passage from Goebel's Organography may here be quoted, which is 

 specially applicable to the present case (Engl. ed., vol. i., p. 60): "Most of our phylo- 

 genetic series are reduction-series, that is to say, are those in which the changes arc- 

 brought about by arrest. There is a simple psychological explanation for this. If we have 

 a definite ' type ' we obtain through it a fixed starting-point for our comparison. But 

 this is wanting when our comparisons deal with an ascending and not with a descending 

 series. It is specially necessary to refer to this, because arrests have frequently been 

 assumed upon the subjective grounds above indicated without definite proof of their being 

 existent. ... It is only our synthetic necessity which forces us always to the assumption 

 of reduction-series, of which, however, many can only claim to be fictions, imparting 

 the aesthetic pleasure of bringing a series of facts into connection with one another." 

 The "synthetic necessity" in the present case has been to bring the large-leaved 

 Ophioglossaceae into line with the definite large-leaved type of the Ferns : the laltei 

 have been constituted a fixed starting-point chiefly because they are well known. 



