of Vascular Strands in Angiopteris evecta. 389 
(though faintly) the characters of an endodermis. It may 
perhaps be urged that this is merely the tangential division of 
tissue which has never yet become adult, but the extreme 
lateness of its occurrence is opposed to such an interpretation. 
It was thought that the anomalous position of the sieve-tubes, 
whichj in Angiopteris as well as in Marat tia, lie outside the 
ptotophloem, might be related to this activity* but we failed to 
find conclusive evidence that such was the case. 
In Marattia , where the same thickening of the parenchyma 
bordering on the stele takes place, though to a much more 
limited extent, only very few layers are formed. The 
endodermis here is usually formed from the innermost layer 
if there is any secondary formation at all. This endodermis 
is a very well marked tissue, and is interrupted here and 
there by curious cells resembling the ‘ passage-cells * met with 
in the roots of many plants. Commonly these passage-cells 
undergo several tangential divisions, but the depth of the 
whole number of cells thus produced does not greatly exceed 
that of the adjacent endodermal cells. 
Passing to the apical region of the stem, in which the stelar 
tissues are in process of differentiation, it is observed that the 
xylem of the leaf-traces is endarch in position, whilst that of 
the larger strands of the stem is inclined to assume a mesarch 
character. This practically confirms Mettenius’s statement 1 
as to the position of the spirally marked elements in cases in 
which they can be distinguished. 
After examining a number of young plants we have come 
to the conclusion that the young stem possesses a single 
apical cell of a large size and of prismatic form, though 
somewhat irregular in transverse section. It sometimes has 
a more or less triangular form when seen from above, and it 
then presents a four-sided appearance. The place of origin of 
the leaves is clearly marked by the large apical cells which 
characterize their early condition. 
The tannin cells which are so abundant in the leaves and 
roots are comparatively rare in the stem, except in connexion 
1 Mettenius, loc. cit;, p. 516. 
