Anatomy of the Ophioglosseae . 385 
as its absorption from the cortex would be interfered with 
by the phloem outside it. Further, this would be com- 
pensated for by the spreading out of the other protoxylem 
into a long, peripheral arc, such as is found in this plant. 
Adventitious buds occur on roots of Ophioglossum pendulum 
and other species. Prantl 1 has observed them in O. lusitani - 
cum, O. coriaceum , O. capense , O. Liters sent , O. ellipticum , 
O. japonicum , O. pedunculosum , O. reticulatum. They may 
possibly occur in most of the species, but Welwitsch 2 notifies 
their absence in O . fibrosum. 
The theory suggested above is purely tentative, owing to 
want of material and of sufficient data. It may be stated 
thus : — The monarch structure in Ophioglossum is an adapta- 
tion for favouring the growth of numerous adventitious buds 
on the roots, in the case of comparatively small and slow- 
growing species, where the supply of nourishment from the 
parent plant is limited. Owing to the monarch structure, the 
assimilated food has to reach the root-tip via the adventitious 
bud, so that the latter may be able to divert all that is 
necessary for its growth. To test this theory it would be 
necessary to observe whether many or few adventitious buds 
were produced in proportion to the size of the assimilating 
surface of the plant ; this is not possible at present, but one 
or two cases may be mentioned. 
O. pendulum produces adventitious buds, but has a large 
assimilating surface, more than ten times that of any species 
in the section Euophioglossum , judging from data of leaf- 
measurements given by Prantl. There is thus presumably 
plenty of material for producing buds in this species without 
putting any restriction on the further growth of the roots 
which form them. And this plant has diarch, triarch, and 
tetrarch roots. 
O. palmatum is also a large-leaved species, having diarch 
roots. 
O. fibrosum would be an exception, as, assuming the observa- 
1 Prantl, 1. c., p. 308. 
2 Welwitsch, quoted by Prantl, 1. c., p. 308. 
