230 THE MICROSCOPE, 
two cannot be separated by their dimensions. This must be done by 
the form and structure of the epidermal appendages. 
Here the colorless, cup-shaped glands already referred to, are 
diagnostic. They are always present on the mature Paulownia 
leaves, sometimes upon the upper surface, sometimes upon the lower, 
occasionally on both. On the upper aspect they are usually most 
abundant about the region near the base of the leaf where the large 
veins meet to enter the petiole. Here they are clustered in a quite 
conspicuous patch of little cups. On the lower aspect they are to 
be found attached to the cuticle of the large veins, often on the 
lateral margins, while they are also noticeable sparingly scattered 
over the basal portion of the general surface. 
When the young leaves are villous with glandular-tipped, un- 
branched hairs, these remain, although they become less abundant 
as the leaf increases in size and age; they never entirely disappear. 
Those on the general lower surface usually diminish somewhat in 
size as well as in numbers, while on the veins they retain most of 
their original characters. The same conditions obtain, to a certain 
extent, with the copiously branching hairs found on many of the 
leaves. These remain in some profusion on the general cuticle, 
while on the veins, glandular hairs are usually developed, as the 
touch will demonstrate. 
The hairs, however, are of less diagnostic value on the mature 
foliage than the cup-shaped glands. The same holds true with 
Catalpa. If the colorless, cup-like appendages are present on 
either surface of the leaf, or on the petioles, the leaf is from the 
Paulownia; if the fleshy, glandular scales exist in the axils of the 
veins below, the leaf is from the Catalpa. With the young leaves the 
hairs must be studied, as the glands are then, on both trees, entirely 
undeveloped or obscure. 
The following recapitulation condenses the matter into the form 
of a key or analytical table : 
RECAPITULATION. 
Ovate-cordate leaves known to be from either Catalpa or Pau- 
lownia (A). 
A Leaves young or immature (B). 
A Leaves mature (C). 
B Lower surface villous with unbranched hairs, not glandular- 
1 CEA ee ed a dar A PPE a ThA Catalpa. 
B Lower surface villous with unbranched hairs, glandular- 
tipped ; a few scattered cup-shaped glands on the veins, Paulownia. 
B Lower surface densely white-woolly with copiously branching 
