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 inay 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 XIIL.). 
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 confparison 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. 
1Mettenius, Hot. Zect., 1867, p. 98; Celakovsky, Préngh. Jahrbs., 1884, p. 291. 
*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 are 
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 latter 
have been constituted a fixed starting-point chiefly because they are well known. 
