120 Brebner . — On the Prothallus and Embryo of 
genus, whereas they are unicellular in the two latter genera. 
It is possible this may be found to have phylogenetic 
importance, and strengthen the view that the Eusporangiate 
Ferns and the Mosses had a not very remote common 
ancestor. 
The exceptional mode of development of the antheridia, in 
certain cases, resulting in the formation of a very small 
number of spermatozoids, is probably due to the antheridium 
as a whole being developed from a cell which was nearly, or 
quite, adult. 
The archegonia present no features which are not likewise 
characteristic of Angiopteris , Marattia , and presumably Kaul- 
fnssia. 
The structure of the growing-point of the stem of Danaea 
seems to be very much in the same condition as in the other 
two genera which have been studied. It appears in fact to 
be still in the transition stage from a single apical cell to 
a group of equivalent initials. It is interesting to note that 
Danaea , which is usually placed lowest in the scale among 
the Marattiaceae, is the genus which presents the clearest 
indications of a single apical cell. There can be little doubt, 
in view of the results obtained, that the Marattiaceae are 
descended from an ancestor whose growing-point presented 
a well-marked single apical cell, that being really the 
primitive type of growing-point throughout for the great 
Fern-series. 
The apical meristem of the cotyledon and subsequent 
leaves does not seem at any time to obviously possess an 
apical cell, and in this also there is agreement with the other 
genera. 
The primary root, until further evidence is forthcoming, 
may be considered to have a single apical cell ; but the 
subsequent adventitious roots have a group of equivalent 
initials, sometimes clearly four. 
The stele, both of the stem, and of the root, has a distinct 
endodermis, agreeing in this with Angiopteris at any rate. 
The root-stele merges directly in that of the stem, the latter 
