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[Vol. 8 
formed, this structure is complicated by the development of vascular strands 
inside the dictyostele, and these ''commissural" strands can be traced up to 
the apical meristem of the stem, and are therefore true cauline strucures. 
As the sporophyte increases in size, the number of leaf-traces increases and 
further commissural strands are also formed, but the greater part of the 
elaborate skeleton of the adult sporophyte is undoubtedly of foliar origin, 
only the relatively unimportant commissural strands being cauline. 
The history of the development of the fibro-vascular skeleton of the 
Eusporangiatae leads inevitably to the conclusion that in the Ophio- 
glossales the whole stelar system is derived from the leaves and roots, and 
this is true to a great extent for the Marattiales, although in the latter the 
commissural strands are really cauline in origin. 
It may be said also that the cortical tissue of the caudex is to a consider- 
able extent of foliar origin, being made up of the coalescent leaf bases. This 
is, to some extent, a confirmation of Delpino's theory that the leaves, instead 
of being appendages of the stem, are the primary organs, and that the so- 
called stem is formed by the coalescence of leaf bases .^^ 
It is also clear that the medullary tissue is in no case of stelar origin, but 
is always a portion of the ground tissue (to use the older term) which is 
more or less completely enclosed by the coalescent foliar steles. 
The great preponderance of the foliar structures over the stem in most 
Filicineae has not received the attention that might be expected, in the 
many discussions on the nature of the stelar tissues that have appeared. 
Few of the higher plants show this to the same extent, and it may be ques- 
tioned whether any Angiosperm can show leaves equal in complexity to 
such ferns as Angiopteris and some of the tree ferns. It is true that the 
leaves of some palms are bulkier, but structurally they are decidedly simpler. 
So far as mere length is concerned, probably some species of Gleichenia and 
Lygodium surpass even the longest palm leaf. Hooker^^ states that Lygo- 
dium articiilatum A. Rich has stipes 50 to 100 feet in length arising from a 
slender prostrate rhizome. 
The very young sporophyte of Ophioglossum, which the writer believes 
to be the most primitive of existing ferns, has no stem at all, but consists 
simply of a single leaf and root, the stem arising secondarily as an adventi- 
tious bud. This is entirely in harmony with the theory of the derivation 
of the Filicineae from Anthoceros-like ancestors; and the predominance of 
the leaf, shown in the young sporophyte, is maintained throughout the 
whole history of the Filicineae. 
The assumption, therefore, that the stem is the predominant or primary 
organ of the sporophyte, and that the leaves are mere appendages of this, 
is hardly borne out by a study of the ontogeny, at least of the Eusporan- 
giatae; and this probably will be shown also to be the case in many, at least, 
of the Leptosporangiatae. 
22 See Schoute, loc. cit., p. 97. 
23 Hooker, J. D. Handbook of the New Zealand flora, p. 385. London, 1867. 
