[kirsco] CERTAIN STRUCTURES IN THE PTERIDOPHYTES 389 
chymatous ” strands and the protoxylem as can be seen from the follow- 
ing (18, 480) :— 
“That these peculiar ‘ Stumpfzellen-Stringe’ stand in close rela- 
tion to the protoxylem, seems to me to follow from the fact that they 
occur only in immediate proximity to them, and that the spiral and an- 
nular tracheids bordering on them possess very irregular thickenings 
(Verdickungsschichten) ;”—“ It is very curious that the ‘ Stumpfzell- 
Stringe’ appear only at curves of the wood in cross section (Holz- 
Querschnittes), and always on the concave side.” 
The presence of these strands is recorded by Terletzki in Cyathea 
medullaris, Osmunda regalis, Blechnum brasiliense, Adiantum formosum 
and Pteris aquilina. They are widely present in the ferns as a whole 
especially in the stipe, less frequently in the stem (rhizome). More- 
over, they occur only where the protoxylem lies at the edge of the xylem. 
“Where the protoxylem is more in the centre of the xylem, as in the 
rhizome of Pteris aquilina, these peculiar ‘ strands’ are not found.” 
Terletzki describes the anatomy of Pteris aquilina fully, and in 
the description of the rhizome the following is found (18, 486). 
‘ Stumpfzellen-Strange,’ as above described, are not found in the rhizome 
of Pteris aquilina; the fact that the protoxylem groups are not at the 
edge of the xylem sheath (Holztheils), may have some connection with 
this.” 
As will be shown below, this is not the case, for definite thyloses 
are found in the rhizome of the common bracken fern, but only in cer- 
tain regions. Moreover, owing to the large amount of starch in these 
cells the sections have to be treated in a certain manner before the struc- 
ture becomes clear. 
The structures are described for the stipe of Pteris aquilina (18, 
492), and are also figured (13, Figs. 8, 9 and 10n). 
The cells here are of the same nature as the ones previously described 
and contain starch like the other conducting cells, showing no traces of 
oil, resin or similar substances. 
According to Terletzki the “ Stumpfzellen-strange ” do not occur 
in the roots of Struthiopteris germanica (18, 473), or in those of Pteris 
aquilina (13, 490). All the work to be described below was done before 
Terletzki’s article was seen, and as no roots were examined in the course 
of the work, no steps were taken to test the validity of this statement. 
At the conclusion of his paper (13, 493, 494), Terletzki states his 
reasons for disagreeing with Dippel as to the contents of the “ Stumpf- 
zellen-Stringe,” and takes Osmunda regalis as his basis of proof. The 
cause of Dippel’s misinterpretation of the function of the cells in ques- 
tion, was the great similarity in appearance of the “ Stumpfzellen- 
