296 Bower . — Notes on the Morphology of 
The divided leaf-trace which they all show confirms the derivative character 
of both lines. 
6. The balance of evidence acquired since 1896 has distinctly favoured 
an alliance of the Ophioglossaceae with the Filicales. It is in the direction 
of the Coenopterideae, and of living Ferns the Osmundaceae, that we may 
look for their true place. 
7. The normal spike of the Ophioglossaceae will, in relation to this 
comparison, and especially in accordance with the anatomical facts, be held 
to be ultimately of pinna-nature ; perhaps in most cases a result of pinna- 
fusion, according to the theory of Roeper. But this unit is subject to 
repetition in Ophioglossum palmatum . 
8. The vascular supply to the Ophioglossaceous spike being normally 
marginal, or from an abaxial pinna-gap, it differs from that to the spore- 
producing organ in the Psilotaceae and Sphenophyllaceae, where it comes 
off from the adaxial face of the foliar strand, or is the middle region of it. 
This difference, if it be found to be constant, may provide a real and valid 
anatomical distinction. 
Note. 
I know only too well the undesirableness of introducing new terms into 
the vocabulary of the science. But any one who has read attentively those 
interesting pages of Professor Goebel’s ‘ Organography’ in which he deals with 
the phenomena of increase and decrease in number of parts in the flower 1 
must have felt the want of some expression which, without connoting any 
detailed view as to the method, shall still convey the conception of increase 
or decrease in number of the parts from that which is regarded as normal 
or typical. The old terms ‘ chorisis ’, ‘ dedoublement ‘ fission 5 , or ‘split- 
ting ’, all have had special applications, and convey meanings relating to the 
method or manner of the increase. In the use of them there is a danger of 
conveying more than the simple conception of increase. ‘Negative chori- 
sis ’ and ‘ ablast ’ suffer under the same disability. The readiest way of 
avoiding such difficulties is by the introduction of some new term which 
carries no preconceptions, and while stating the fact does not imply any 
method. I venture therefore to suggest that the term ‘ pleiogeny ' should 
be used to connote those phenomena which involve increase in number of 
parts beyond the normal or typical. The term ‘ meiogeny ’ would similarly 
connote a decrease from the normal or typical. 
It is not only in the case of floral structure that such terms may apply. 
In the present case it would be a phenomenon of ‘ pleiogeny ’ that we have 
been studying in Ophioglossum palmatum. And similarly the increase of 
sori so frequently traceable in Ferns would be a phenomenon of the same 
class. Having recognized this, the next step will be by comparison and 
1 English Edition, pp. 52S-42 
