128 BOTANICAL GAZETTE [FEBRUARY 
The growing region resembles that in any root. In a few milli- 
meters at the apex there is a meristematic region of actively 
dividing cells. Then there is the region of elongation and differ- 
entiation. The origin of the different layers would seem to con- 
form to the general situation in monocotyledons, with distinct 
initials in calyptrogen, dermatogen, plerome, and periblem. This 
would be in contrast to the situation in Thismia Versteegii, where 
Ernst and BERNARD report a common initial for epidermis and 
root cap. In Thismia americana the tip region of the root is free 
from fungi, but the tissue formed is rapidly invaded by the mycelium 
from older parts. In no case was new mycelium seen to penetrate 
the epidermis and so enter the uninfected region, as reported by 
JANSE in Thismia clandestina (T. javanica J. J. Sm.). 
Compared with that of the root, the anatomy of the floral axis 
is complex (figs. 8-10). Here the vascular elements are arranged 
in a cylinder of 3-6 bundles. In the early stages the number is 
very apt to be 3; in the older axis, near the apex, there are divisions 
of the original bundles, giving a larger number, frequently 6. More 
may be seen where branches go from the original bundles. 
Each bundle consists of definite xylem elements and a mass of 
cells with slightly thickened walls (fig. to). The xylem is slower 
to appear than the latter, which are early clearly distinguishable 
(fig. 8). In mature parts, the small clear cells appear in the same 
relation to xylem as phloem usually does, but they show no sieve 
plates so far as can be determined. Nevertheless, it seems probable 
that these elongated cells function as phloem. The xylem vessels 
have lignified and spirally thickened walls and their number varies 
from 2 to 15 in each bundle. The large number, the conspicuous 
spiral thickenings, and the lignification, as well as the greater and 
more definite phloem development, are quite in contrast to the 
condition found in the root. | 
A single strand of a few xylem vessels and phloem cells supplies 
each of the bractlike leaves (fig. 11), which are very thin and rela- 
tively broad. There are also branches of the main cylinder sup- 
plying the floral parts and producing the conspicuous nervation of 
the perianth. 
There is no definite endodermis or pericycle in the floral axis, 
