MYCORHIZA AND REDUCTION 241 
the Pteridophytes, leads to a general reduction of the infected sporophyte 
as a whole. 
The particular family in which the argument relating to mycorhiza has 
been specially applied is the Ophioglossaceae. A more detailed account 
of it will be given where the family is specially described below; but 
meanwhile it is to be noted that there is throughout the Adder’s Tongues 
a close parallelism of proportion of the sterile lamina to the fertile spike : 
this is indeed one of the most remarkable features in the morphology of 
the family, the parallelism extending not only to the size of the respective 
parts, but also to the character and extent of the branching of each. If 
saprophytic nourishment by the mycorhiza were in this case a real 
substitute for chlorophyll-assimilation the sterile lamina would fall behind 
the spike in its dimensions; but in the normal representatives of the 
family it does not. The conclusion follows that in the mature sporophyte 
of the Ophioglossaceae the mycorhiza is not functionally an effective 
substitute for nutrition by chlorophyll-assimilation. 
There is, however, one series of species in that family in which the 
proportion of the two parts is not maintained, viz., the section Ophioderma 
of the genus Ophioglossum. Here the epiphytic O. pendulum shows 
approximately the usual balance; but in O. zutermedium, a land-growing 
species, the sterile lamina is relatively small, while in O. simplex, also a 
ground-growing species in which mycorhiza is present, the lamina appears 
to be altogether unrepresented. I regard this section, Ophioderma, as a 
series in which mycorhiza has become effective as a substitute for chlorophyll- 
nutrition, and that reduction of the vegetative system has actually followed 
as a consequence: nevertheless the spike, being effectively nourished, 
retains its dimensions. But disturbance of the balance of the vegetative 
and reproductive systems such as. this is a very different thing from any 
general reduction of both, such as is sometimes assumed to follow in 
consequence of a symbiotic habit.! 
Another family which provides an interesting parallel in this respect to 
these Ophioglossaceae is that of the Psilotaceae. In Zimesipterds there is a 
reasonable balance of size between the forked sporophyll and the bilocular 
synangium. In Psi/otum this balance is not maintained, for the small 
sporophylls are ineffective as assimilating organs while the trilocular 
synangium is still of large size. It is true the green axis is an effective 
organ of assimilation, but it would appear probable that the mycorhizic 
state also assists. 
The discussion of the parts played respectively by amplification and 
reduction in the genesis of the homosporous sporophyte may now be 
summed up. The end of its development is the production of the 
largest number of effective germs. To increase their number involves 
amplification of the propagative system. This involves also in many 
cases amplification of the nutritive system. However, this is not an 
1See Scott, Studies, p. 511. 
Q 
