No. 459.] ANATOMY OF CATALPA HYBRIDS. 121 
growth much longer and narrower. Tracheids of the summer wood nar- 
row, spiral, scalariform, and pitted, and showing all transitional forms from 
simple spirals to hexagonal bordered pits in ı-3 series. The radial walls 
of the vessels with numerous hexagonal pits having rather large, trans- 
versely oval or oblong openings. 
Tangential.— Medullary rays rather numerous, resinous, low to medium 
and 1-3, chiefly 2 cells wide; the cells rather thick-walled, hexagonal. 
Tangential walls of the vessels with numerous and variable, transversely 
oval, oblong or long linear, often simple pits. The tangential walls of the 
spring parenchyma with numerous round or transversely oval, chiefly simple 
pits; those of the early spring wood cells with transversely linear, narrow 
and rather numerous pits. 
A comparison of the transverse and tangential sections for 
this species, with those for the hybrid, makes the general rela- 
tions of the two very obvious, but a more critical examination of 
them is necessary. In each case the wood is characterized by 
the great breadth of the growth ring. In C. kempferi, the thin- 
walled spring wood constitutes a rather narrow zone representing 
but a small volume of the total growth for the season. Precisely 
the same is also true of the hybrid with the difference that the 
volume is reduced to about one half what is to be found in the 
former, showing the definite influence of one parent. In each 
case the wood parenchyma is confined to the composition of the 
vessels or to the earliest spring wood, and there is no feature in 
them which can be directly ascribed to C. &emfferi. A very 
definite connection between C. kempferi and the hybrid, appears 
in the distribution of the tracheary tissue which, in the latter, 
forms a well defined limiting layer occupying the same position 
as in the former but characterized by greater uniformity of width. 
This is undoubtedly due to C. kempferi in the first instance, but 
ultimately it is to be regarded as a resultant effect from the 
interaction of the two parents as will appear later. In addition 
to the limiting zone of tracheids which sometimes extends radi- 
ally inward as in C. kampferi, though not generally to the same 
extent or so frequently, it is to be noted that in the hybrid there 
is a second and more internal zone of tracheary tissue which cen- 
ters in the small vessels of the outer summer wood and which 
forms tangentially extended tracts of a very well defined char- 
acter. This feature is one of the most prominent structural 
