366 Bower. — The comparative examination of the 
daceae, and Marattiaceae form a natural series, the last named 
being the most complex. 
(2) That in respect of reference of the sporangium to one or 
to more than one initial, the Osmundaceae are intermediate 
between the leptosporangiate and eusporangiate types, and 
that therefore this distinction cuts through a natural series of 
plants. 
(3) That the increase of complexity is accompanied by a 
sinking of the centre of construction, similar to that already 
noted in the apices of root, stem, leaf, and wings of the leaf of 
the above series. 
(4) That the change in form of the archespore (from the 
conical in the leptosporangiate Ferns to the cubical in the 
eusporangiate) is similar to the change of form of the initial 
cells of root, stem, leaf, and wing, observed as we rise in the 
above-named series. 
(5) That the structure of the wall and tape turn is more 
complex in the eusporangiate Ferns, and the number of 
spores in each sporangium is larger, while the sporangia them- 
selves are fewer. 
(6) That no difference of importance in the sporangium is 
to be found between the filmy and the robust types of the 
Osmundaceae. 
Conclusion. 
A comparative study has now been made of each of those 
meristematic tissues which contribute to the formation of the 
sporophyte of the Fern, viz. of Root, Stem, Leaf, Wing, and 
Sporangium. Each of these has been examined in representa- 
tives of various divisions of the Filicineous series, viz. in the 
Hymenophyllaceae, Polypodiaceae, Cyatheaceae (in part), 
Schizaeaceae, Osmundaceae, and Marattiaceae. The main 
result is to demonstrate a singular parallelism in character of 
all the meristems in these several divisions, and to show 
that in the divisions first named the meristems are relatively 
simple in construction, and exhibit definite regularity of seg- 
mentation, one initial cell of definite form being present in 
