252 ORR—TRACHEAL “TISSUE IN CAPPARIDACEAE. 
2. Cappareae. 
Among the included genera of the Cappareae various types 
of tracheal envelopes are represented, differing in detail from 
one another, but all easily distinguishable from those of the genera 
already described.in one definite feature. In Cleome and its 
allies the thickened bands are found on the periclinal or surface 
walls of the tracheides, and so are easily seen in surface view 
under the microscope; but in Capparis and its associates it is 
the anticlinal or lateral walls of the cells which are strengthened, 
while the surface walls remain unthickened. Notwithstanding 
the varieties of structure represented in the Cappareae, this 
anatomical feature would appear to indicate definitely the limits 
of each tribe, and to form a distinctive mark between them. 
In the Cappareae this thickening of the anticlinal walls of 
the tracheides takes the form of spirals or reticulations, which, 
on account of their disposition, present an appearance in surface 
view of irregular lobes or protuberances on the lateral walls.* 
In many of the types this configuration is often the most char- 
acteristic, for, owing to the extreme shallowness of the cells, 
the fact that these lobes represent the end views of thickened 
bands, which are continuous to the base of the cell, can only be 
observed by careful focussing, or by means of sections. In 
other cases, and particularly in some species of Capparis, the 
depth of the tracheides is such that the slightest _ciaesa he is 
sufficient to bring the lateral walls into surface view 
In the figures illustrating the different types of envelopes, 
the thickening of the anticlinal walls as it appears in surface 
view has been indicated in each case, as this configuration 
seems to be more or less typical of each genus examined, and is 
expressive of the extent of the thickening over the surface of 
the walls, which cannot always be seen from this point of view. 
Under Capparis decidua, Pax, a diagrammatic representation 
of an individual tracheid has been figured to illustrate the deeper 
type of element with reticulate thickening on its lateral walls. 
This deeper type of tracheid is best seen in Capparis, and the 
lateral walls can be easily flattened out, thus enabling the 
observer to determine the nature of the thickening. For this 
reason the sheath characters of this genus will be described first. 
Capparis, Linn. 
Among the different species of Capparis examined, both the 
deep and shallow types of tracheal elements are represented, 
his descriptions of the structure of the seed-coat in certain species of the Gen- 
tianaceae (Journ. de bot., xviii, 1904, pp. 37-52). . 
