74 
Cormack. — On a Gambia l 
process of development in the node, as illustrated in Fig. 6, 
has continued for some time. 
Thus it is seen that in the Equisetaceae the development 
of wood later than protoxylem begins in the node, and after- 
wards extends through the internode. 
We now proceed, to examine certain inferences which have 
been drawn from the known structure of Calamitae, to adduce 
evidence, and to draw conclusions as to the course of develop- 
ment of the vascular system in these plants for purposes of 
comparison with what we have seen in Equisetaceae. 
Fig. ii, from a transverse section of a young Calamite, 
shows a bundle and part of the interfascicular tissue, as also a 
portion of the rind with the cambial layer crushed and 
distorted, but still recognizable, and showing its connection 
with the inner tissues. 
There is some difference of opinion as to the nature of the 
canal found at the inner angle of each woody wedge. Re- 
garding these canals, Williamson writes 1 : ‘Mr. Binney . . . 
. . . was doubtful respecting their nature. He says that Dr. 
Hooker, “ after carefully examining these openings, I believe, 
came to the conclusion that they were passes for a peculiar 
kind of tissue which has unfortunately been destroyed, rather 
than the mere cavities which we now see in the specimens.” 
This supposition, however, is certainly not correct.’ 
Schenk, who would place the Calamitae in question among 
the Gymnosperms, gives a figure 2 in which phloem takes the 
place of the cavity, and the adjacent medullary tissue is 
described as xylem ; thus the cambium and the tissue formed 
from it (Fig. n) would have to be considered as extra- 
fascicular. Solms-Laubach 3 has seen the original preparations, 
and asserts that they are badly preserved and do not justify the 
explanations given ; and to his view Schenk has given assent 4 . 
Fig. io represents another part of the same preparation 
from which Fig. n was drawn, and shows the remains of the 
protoxylem occupying the canal. The rings marked x are 
1 loc. cit. p. 485. 2 Zittel, Handbuch der Palaontologie, p. 237. 
3 Fossil Botany, Eng. Ed,, p. 297. 4 Handbuch der Botanik, vol. IV, p. 109. 
