320 BOTANICAL GAZETTE [May 
same root at different places, I noticed that the collapsing of the 
cortex does not take place in the entire length of the root, but only in 
the basal (thickest) portion. The occurrence of rhapidines is very 
variable; in some roots they were observed only in the younger 
apical portion; in others they were found also in the basal. 
‘The lateral roots of the first order show the same structure as the 
mother root, but the number of strata in exodermis and cortex is _ 
generally smaller. The exodermis, for instance, may be represented 
by only a single layer, but sometimes three are found, as in the mother 
root. The cortex may be solid or collapsed, and may be reduced to _ 
only three strata. The epidermis does not differ from that of the 
secondary root, and is glabrous. The endodermis is thin-walled, 
and the secondary formations are usually not so advanced but that 
the primitive organization may be readily observed to be diarchic or 
tetrarchic. 
A corresponding structure is to be found in the lateral roots of the 
second order. They are capillary and have a glabrous epidermis 
and an exodermis of two layers. The cortex consists of three thin- 
walled strata, which are collapsed at the base of the root, but entire 
near the apex. Inside the continuous pericambium are a few stereo- 
matic cells, mostly only two, diametrically opposite each other. The 
leptome is represented by two broad strands alternating with two 
rays of hadrome with two wide reticulate vessels in the center, and 
about three scalariform outside. No secondary growth takes place 
in these roots. 
If it were not for the presence of raphidines, the root of Dianthera 
would be utterly unlike that of Ruellia described above. Moreover, 
the habitat of Dianthera is naturally the cause of the very different 
development of exodermis and cortex, and of the absence of cystoliths, 
sclerotic cells, and crystals. 
THE STEM 
The rhizome with the stolons and the ascending aerial shoots 
show the same structure in general, and, as stated above, the*axis is 
polystelic.** This peculiar structure was observed in all the” inter- 
tr A polystelic stem is also possessed by Dianthera crassifolia Chapm. and D 
Janceolata (Chapm.) Small, but not by the following species: D. comata L. (Porto 
