No. 459.] ANATOMY OF CATALPA HYBRIDS. 127 
small, transversely oval, and simple pits, or 2-seriate hexagonal bordered 
pits. Radial walls of the cells of the summer wood commonly with small, 
lenticular pits showing a cross. Radial walls of the vessels with multi- 
seriate, hexagonal or even transversely oblong, distant pits, the thyloses 
with distant, linear and simple pits. 
Tangential.— Rays rather narrow, medium to somewhat high, upwards 
of 3-seriate, the cells all thin-walled, hexagonal. Tangential walls of the. 
vessels with multiseriate, oval pits, the narrow, linear orifice of which is 
transverse and often exceeding the pit. Pits on the tangential walls of the 
spring wood parenchyma often simple and transversely oblong. 
The growth rings of C. bignonioides are seen to be very broad, 
thus conforming to what also appears characteristic of C. kæmp- 
jeri, and what arises as a necessary resultant in the hybrid, but 
constituting a feature entirely wanting in C. speciosa. Thus it 
appears that the growth rings in C. speciosa are approximately 
only one fifth of the radial dimensions in either the hybrid or C. 
bignonioides. While in general terms this difference may be 
said to exist, it cannot be taken as a differential character of 
leading importance for the reason that under certain circum- 
stances of growth, the hybrid may develop equally narrow 
rings. Putting this factor to one-side, we then find that the 
structure of the growth ring affords a very definite means of 
determining any possible relationship. The region which I con- 
sider as probably representing the spring wood, is several times 
broader than in C. kempferi, and the contraction of this zone in 
the hybrid must be viewed as due to the direct influence of the 
latter species, The vessels of the early spring wood are large 
and they increase in size for some distance within the limits of 
the spring wood, so as to form a rather broad zone without any 
well defined distinction of a primary and secondary zone as 
appears in C. kempferi and more prominently in the hybrid, and 
it is probably correct to say that the limitation in size and dis- 
tribution which is expressed in the latter, is the direct result of 
the dominating influence of the large vessels of C. bignonioides. 
The influence of the latter is also expressed in the general dis- 
tribution of the vessels. In C. kempferi, C. bignonioides, and 
the hybrid, the vessels gradually diminish in size toward the 
outer limits of the growth ring, but à comparison of their dis- 
tribution in the first and last shows that the hybrid occupies an 
