meristems of Ferns as a Phylogenetic Study. 317 
initial cells are less inclined to one another than in the Poly- 
podiaceae, etc., in which the construction is on the confocal 
type, and the initial cell or cells are thus deeper. Again, the 
apices of the cells are often truncate, the form of the initial 
cells being thus not pyramidal but oblong, as is the case in 
the coaxial type : in both these characters, which are, as above 
pointed out, to be connected with a lowering of the centre of 
construction , the roots of the Osmundaceae, and more espe- 
cially of Todea , approach the Marattiaceous type. 
While drawing this distinction between the two types of 
construction, and while recognising that the Marattiaceous 
type is consistently coaxial, it is to be remembered that a 
pure and consistent coaxial construction is exceptional and is 
found exemplified in the Marattiaceous type and in the 
Janczewski’s fourth type of Angiospermic roots ; the large 
majority of roots are mixed in the character of their meristem : 
thus in the leptosporangiate Ferns the construction of the 
root-cap is coaxial, while that of the body of the root is con- 
focal : in the Gymnosperms the confocal character is limited 
to the plerome, while all the outer tissues are coaxial : in the 
Monocotyledons the whole is confocal with the exception of 
the root-cap. It has, however, been pointed out by Dr. G. 
Karsten 1 that in the development of certain individual roots 
there may be a transition from the coaxial type in the early 
stages, to the confocal in the older root : observations such as 
these show that too great importance should not he attached 
to these characters alone as defining natural affinities ; but, on 
the other hand, if there be traceable in a series of forms a 
sequence of character of the meristems which follows the 
series as laid out on other grounds, the meristematic cha- 
racters may well be used as strengthening the systematic 
conclusion ; and this is the way in which such evidence is to 
be used in the Filicineous series 2 . 
From the comparative study of the meristems of roots of 
1 Ueber die Anlage seitlicher Organe. Leipzig, 1886, pp. 6-8. 
2 See conclusion of this paper. 
