[Kirsch] CERTAIN STRUCTURES IN THE PTERIDOPHYTES 
such identical structures should be present in the ferns of the coal mea- 
385 
sures as well as in existing forms is not at all strange, for this appear- 
ance depends solely on the state of maturity of the cell and not on any 
special function. 
In an examination of sections taken through some mature pinnæ 
it was observed that the canals were well marked and filled with thy- 
loses, as in the stipe itself. 














(2\ 
ao 
\ Soo) elt 
| = = 
° — ea 
ALES ES => 
e ss = 
la Ne EP ENT 
7 7 = aad 
o|| Sa = LENS 
ol ==. => 
NET a ives 
Sm — 
olf 0 al = Es 
9 = Soe mie PO ee 
g A = =| 
este 
= ES 5° 
° = a ee 
A [SS 22 
A =| = 2 
= A ONE 
2 A 2: 
== = 
À S LE} od net ---Ky 
é | = 
L—] = S 
À = 22 
ea a 
L—] TT = 
= = 
SS => 
a Al 
= = 
= 
— Es 
\ 
[ass] A 
: => 
— 
Fig. 15.—Pteris aquilina, stipe, Oct. 19th, 1906. Longit. 
thyloses in canal. 
Showing thick-walled 
X 490. 
Some of the walls exhibiting pitted markings, Pth. 
ramifications of the frond, and this is to be expected in view of its 
probable function. The nature of this function will be discussed at the 
close of this paper. 
The above ends the description of the organs of Pteris aquilina 
Sec. IV., 1907. 24. 
D uni 
The structure thus extends through all the 
