Comparative Anatomy of the Casuarineae. 255 
doubt different from those in the internode, and may deter- 
mine the type of element produced. The researches of 
Prunet 1 illustrate this point, for he observed that, in certain 
plants showing a distinction between nodal and internodal 
structure, this distinction does not occur in the underground 
part of the stem. 
Remarks on the Structure of the Stem in the 
CUPULIFERAE. 
A glance at the structure of some members of the Cupu- 
liferae, which indeed show some affinity in their anatomy 
with Casuarina , will be of interest. Taking just four genera 
for this purpose, we see that though there is diversity of 
structure in each of these, there is considerable agreement 
in the ground-plan. 
Looking at Quercus first of all, we find this plant, in its 
general structure, to bear considerable resemblance to Casua- 
rina. The vessels with a tendency to form several perfora- 
tions are found chiefly near the protoxylem. Most of the 
others have a single perforation. There are tracheides, and 
transitions from these to vessels. Fibrous tracheides form 
the bulk of the wood. The parenchyma is very well de- 
veloped. 
In Fagus the vessels have both one and several perforations, 
the former the most frequent. Strasburger 2 states with 
regard to the end-walls of the vessels that the least oblique 
have a single perforation, the more oblique a ladder-like or 
reticulate perforation ; while there are some with both bor- 
dered pits and perforations, and others with bordered pits 
only. As in Quercus , there are short, oblique walls in the 
sieve-tubes of one to three plates. 
Carpinus Betulus , L., has vessels with both kinds of per- 
forations. The great majority, however, are of the ordinary 
dicotyledonous type, with a single perforation. But next to 
1 Prunet, Ann. Sci. Nat. Bot., 7 ser. tome XIII, 1891, p. 297. 
2 Loc. cit., p. 273. 
