490 The Botanical Gazette. [December, 
heart shape to almost triangular. In organs which are not 
circular, the lateral diameter is generally the greater although 
the exact reverse is the case in a few species. In the major- 
ity of organs the length is generally about twice the diameter; 
a few however were found in which the diameter was equal to 
the length. 
5. The epidermis is fairly well developed when compared 
with the adjacent epidermis, and we// developed when com- 
pared with the remainder of the motor organ tissue. The 
cells are shorter in the longitudinal direction than those of 
the leaf or petiole and their longest diameter is generally in 
the radial direction. The epidermis is generally covered Fs 
with trichomes: but in no instance could any stomata be found 
within the limits of the motor organ. The hypodermal cells 
are always smaller than the parenchyma cells of neighboring 
parts. They are always very short in the longitudinal direc- 
tion, while the radial and tangential dimensions are some- 
times equal to each other, but as a general rule the radial 
dimension is the greater. The cell walls are generally 
thicker than the walls of the adjacent parenchyma cells, and 
the protoplasm always occupies the periphery of the cells. 
The cells may be arranged in quite regular longitudinal rows, 
or on the other hand the arrangement may be quite irregular. 
The hypodermal tissue is to be regarded homologous with the 
mesophyll of the leaf. There are three types of hypodermal 
cells: (a), the parenchyma type; (4), the collenchyma type 
or those which show thickened corners in the cross section, 
(c), a type intermediate, in which the cells have walls that 
are uniformly thickened. 
6. Very few intercellular spaces could be detected and 
these only near the central stele; they are very small when 
compared with the intercellular spaces of adjacent parts. 
7. The completely developed organ is always traversed by 
a stele which is entire and completely surrounded by a layer 
of non-lignified bast fibers. The meristele, in those leaves 
with primary organs, arises from the axis as three separate 
strands; these fuse to form the meristele of the organ and 5° 
close is the union that it is impossible to make out these three 
in the crosssection. The same may be said of the stele of the 
secondary organ which is simply a branch of the meristele of 
the petiole. The stele may be central, or pushed to one side, 
in which case it is excentric. The remnant of the pith may 
