West. — A Contribution to the Study of the Marattiaceae. 401 
roots certain of these lateral segments assume a function equivalent to that 
of the mother-cell from which they have arisen (cf. Bower, 5 , PL IX, 
Figs. 30, 31, and 32). Segments are also cut off from the distal end of 
these cells ; these apparently go to form the root-cap. 
Histological Notes. 
The histological details of the structure and development of the 
vascular tissues in the young sporophyte have already been critically 
examined by Campbell (20 and 21 ) ; recapitulation of the facts by the 
present writer, whose observations, extending over several hundred serial 
sections of young sporelings of Danaea alata , Sm., and Danaea nodosa , Sm., 
entirely confirm those of Campbell, would therefore be quite superfluous. 
However, since several points of interest have arisen from the present 
investigation on the histology of Danaea , especially with reference to the 
older sporophyte, a few notes on the more important details are set forth 
below. 
As in all other known genera of this family, the anomalous position 
of the protophloem, first pointed out by Shove ( 58 , p. 322, PI. XXIX, 
Fig. 28), was very obvious in every species of Danaea examined by the 
present writer. 
The protoxylem of the stem-meristeles is generally mesarch, occa- 
sionally endarch, whilst in the leaf-trace meristeles it invariably occupies an 
endarch position. 
Even in quite old plants of Danaea the cells of the ground-tissue are 
capable of reassuming meristematic activity ; this fact was clearly shown 
in the case of an adult plant of Danaea alata in which the conducting 
tissues of one of the stem-meristeles had completely decayed away, 
probably as the result of fungal attack working up from the decayed basal 
region of the rhizome. The cells immediately surrounding this meristele 
had become actively meristematic, and had produced around it a continuous 
layer of periderm-like cells, the walls of which, however, were unsuberized. 
1. Endodermis. 
Whilst it is not proposed to attempt to enter upon a lengthy dis- 
cussion of the real significance of the endodermis in the Marattiaceae, a few 
remarks upon the peculiar distribution of this morphological layer in the 
genus Danaea may not be out of place, especially as certain botanists (e.g. 
Jeffrey) have assigned to it far-reaching importance in questions of stelar 
anatomy. 
For the sake of brevity, the statements which have already been 
published as to the presence or absence of this layer in the various genera 
of Marattiaceae are briefly summarized in the following table : 
