No. 459]. ANATOMY OF CATALPA HYBRIDS. 123 
whole, more scattering in the hybrid than in C. kempferi, a 
feature undoubtedly derived from the other parent. The med- 
ullary rays offer no evidence of value in favor of either parent, 
since in each case they present the same features of structure. 
In the structure of the medullary ray as presented in radial 
section, some features are worthy of consideration. The gener- 
ally short, isodiametric cells of C. kempferi are more commonly 
replaced in the hybrid by longer and very variable cells, the 
upper, lower, and terminal walls of which are marked by fine 
pits, all of which features must have been derived from another 
parent than C. kempferi in which the walls are distinguished by 
coarse pits. While in the latter species the pits on the lateral 
walls of the cells are rather large and oval, in the hybrid they 
become small, numerous, and unequal. In each case the spiral 
and scalariform tracheids of the summer wood show transitional 
forms leading to the development of pits, but while in C. kæmp- 
feri these latter structures are hexagonal, bordered, and in 1-3 
series, in the hybrid they are usually simple and in ı-2 rows 
only, thus showing a modification which must be attributed to 
the other parent. 
In a tangential section the medullary rays correspond in 
approximate number and height, as also in the number of 
series of cells entering into their composition, but while in C. 
kempferi the cells are rather thick-walled and hexagonal, in the 
hybrid they are rather thin-walled and oblong, the marginal cells 
becoming much higher and more variable. From this compari- 
son it is obvious that C. kempferi has influenced the hybrid in 
very definite ways, while it is equally clear that the latter pre- 
sents a number of characteristics which could have been derived 
only from C. speciosa or C. bignonioides, and in order to deter- 
mine which, we may next compare C. speciosa. An inspection 
^ of a transverse section of this wood shows that it possesses 
features of structure which are in very marked contrast to what 
may be found in either of the preceding species, but in order to 
make these differences clear, a diagnosis may be given before 
proceeding to a detailed comparison. 
