547 
Origin of Medullation in the Ophioglossaceae. 
the leaf-trace in the young plant of Botrychium may pass off without intrusion 
of a foliar pocket, there being a clear demarcation by endodermis of the 
parenchymatous pith, which is already present, from the parenchyma asso¬ 
ciated with the leaf-trace. But at the insertion of the stronger leaves the 
endodermal barrier encroaches inwards, as suggested by Fig. 9, and it 
appears still more clearly in sections from other plants. Thus an addition 
may be made to the already existent pith. But as the plant becomes 
established, the barrier between the two components of the ultimate pith 
column is no longer maintained, for the intrusive endodermis is often 
imperfect, while there is also some evidence of formation of endodermis 
de novo in relation to the departure of the leaf-trace. It is probably this 
intrusive endodermis, whether originated simply by involution, or by forma¬ 
tion de novo , which was observed by Van Tieghem, and the drawings of 
B. Lunaria and of O . Bergianmn by Poirault apparently show the imperfect 
remains of that morphological barrier. The ontogeny is to be taken here 
as a true guide to the origin of the condition seen in the mature plant. 
From it we learn that an intrastelar pith was first initiated, and that 
subsequently foliar pockets, with ultimately a cortical intrusion, encroached 
upon the pith, and added to its bulk. 
A comparison of the results thus obtained for the Ophioglossaceae 
with the description given by Faull for the seedlings of Osmunda cin- 
namomea shows an essential similarity. 1 In the first place he records 
(loc. cit., p. 525) the occurrence of isolated tracheides in the pith within the 
internal endodermis of O. cinnamomea . Unfortunately he does not figure 
them, but states that they are surrounded by a ring of endodermal cells, and 
suggests that they have been { pinched off ’ from the stele. But are they not 
more probably to be compared with the medullary tracheides of Botrychium , 
and especially of B. ternatum (PI. XLVI, Figs. 18-20) ? In that case they 
would appear to be vestigial evidences of degeneration of the xylem. Their 
existence seems clearly to favour a view involving intrastelar medullation. 
All Faulks observations of medullation in the seedlings of O. cinnamomea 
up to the twelfth leaf deal with changes which are purely intrastelar. The 
ring fence of the outer endodermis is uninterrupted, and shuts off the cortex 
from any connexion with those parenchymatous tracts which occupy the 
stele. The twelfth leaf of the seedling (Faulls Fig. 14)still shows the barrier 
complete. In point of fact, his drawings and descriptions furnish a demon¬ 
stration of the origin of an intrastelar pith, and would never have been 
recognized as anything else, but for the influence of Professor Jeffrey’s 
comprehensive theory of intrusive pith, with which I propose to deal later. 
The drawings and description of Faull show further in the seedling of 
O. cinnamomea that the pith originates partly from intraxylic parenchyma, 
partly from the conjunctive parenchyma with which the intraxylic pith 
1 Trans. Can. Inst, vol. viii, 1909, p. 515, &c. 
