360 Bower . — The comparative examination of the 
that filmy wings may be produced by various modes of 
marginal segmentation. 
Sporangia. 
Much more attention had been paid to the comparative 
investigation of the origin and development of the sporangia 
of Ferns, than to the other meristematic tissues, and I have 
but little to add to the facts already published elsewhere 
on this subject : nevertheless, in order to bring observations 
on the sporangia in line with the facts above detailed, and to 
show that the progress of other meristems from the simpler 
to the more complex as we pass along our series, runs parallel 
with a similar increase of complexity in the origin and 
construction of the sporangium, it will be necessary briefly 
to sketch out the characters of the young sporangium in the 
series of Ferns above cited. 
On the ground of the mode of origination of the sporangium 
from a single superficial cell, or from a number of cells, Goebel 
has distinguished leptosporangiate from eusporangiate forms : 
and I shall show that this distinction, which divides a very 
natural series of plants, is in itself by no means a sharp line 
of demarcation. In drawing this distinction, however, Goebel 
has laid his finger upon a far-reaching difference of character, 
which finds its reflection in every meristematic tissue of the 
plants in question : in roots, stems, leaves, and wings, as well 
as in the sporangia, an increase of complexity of construction 
is to be seen as we pass upwards through the series of Ferns. 
Without entering on details as to the exact succession of 
segmentations of the young sporangia, it will suffice for our 
present purpose to note that the sporangium of the Hymeno- 
phyllaceae 1 , and Polypodiaceae 2 , and other leptosporangiate 
Ferns arises typically as an outgrowth of a superficial cell. The 
first division in this cell is transverse in the Polypodiaceae 3 , 
1 Prantl, 1 . c. p. 39 : also Plate VI. 
2 Reess, Pringsh. Jahrb. v, p. 222. Kny, Parkeriaceae, p. 49. 
3 Reess, 1 . c. Plate XXI, Figs. 4, 5, 7. 
