meristems of Ferns as a Phylogenetic Study. 323 
to any one of the ordinary types of construction. Here we 
have one of those strangely irregular arrangements analogous 
to those which have already been observed in the root, and a 
comparison of this with the apices of stems of the Marattiaceae 
described below will show the same similarity to the latter as 
has been traced in the root. It is to be noted however that 
the large majority of apices of the stems of Osmunda conform 
to the ordinary leptosporangiate type, and such examples as 
that shown in Fig. 25 are the exception rather than the rule. 
The meristem being thus at times irregular, as seen in sur- 
face view, and the subdivision of the segments being variable, 
it is to be expected that the study of it in longitudinal section 
would present difficulties, and I have not been able to trace any 
definite and characteristic mode of segmentation. Longitudinal 
sections cut from a considerable number of stems show that 
a conical apical cell is usually present (Fig. 26), which is 
rather deep in proportion to its height : the relations of 
the surrounding tissues, and their reference to regularly 
succeeding segments are difficult to recognise. Thus it is 
seen both from transverse and longitudinal sections that, 
though the presence of a single initial cell may be ascertained 
in most cases in the stem of Osmunda , it is not always present, 
and the apical meristem is of a less regular and definite type 
than in the leptosporangiate Ferns. 
Taking next into consideration the apex of the stem in the 
Marattiaceae, it may be noted that various accounts have 
from time to time been given of its structure 1 . Holle 2 ascribes 
to the apex of Marattia an elongated, four-sided apical cell : 
in Angiopteris he says that he cannot with certainty track the 
whole meristem as originating from a single initial cell, though 
he thinks that such an origin is probable. 
Some years since I had the opportunity of examining the 
apex of one well-grown plant : a conical cell was recognised 
1 Hofmeister, Abhandl. d. K. Sachs. Ges. d. Wiss. 1857. Compare also De 
Vriese and Harting, Monogr. d. Maratt. pp. 49, 51. The papilla marked {£) 
which is there regarded as the apex of the stem, appears to be part of a young leaf. 
2 Bot. Zeit. 1876, p. 218. 
Z 
