176 BOTANICAL GAZETTE [MARCH 
the primary root are the only underground organs that winter over, 
and by which the future development of aerial floral shoots is secured. 
The term “ pseudo-rhizome” seems very applicable to the subter- 
ranean stem of this and other species of the genus. It was originally 
suggested by Hyatmar Nitsson’s and intended for herbs “in which 
the basal, subterranean portion does not die off with the aerial, but 
stays active and produces a floral shoot the succeeding year by means 
of a lateral bud; and in which this basal portion becomes able 
to increase in thickness and to nourish the over-wintering bud, and 
also to develop secondary roots; such a subterranean stem represents 
a pseudo-rhizome.”’ 
The roots.—The primary root persists for several years, and evi- 
dently as long as the individual lives. During the first season second- 
ary formations in the stele commence, but the growth is rather slow 
and causes neither the cortex nor the epidermis to be thrown off. 
The epidermis thus remains intact, is slightly thickened on the outer 
cell walls, and is almost glabrous. There is no exodermis, and the 
cortex represents a compact tissue of about five strata in which cells 
with raphides are scattered. The endodermis is thin-walled and 
readily distinguished by the small lumen of the cells when compared 
with those of the adjoining cortex. The pericambium is also thin- 
walled and continuous and does not yet (August) show any cell 
division; but there are additional vessels inside the leptome, so that 
the primitive structure of the stele is no longer to be observed; the 
medullary rays are very narrow, consisting only of one row of cells. 
The lateral roots of the first order are almost capillary, and the 
thin-walled epidermis shows many hairs. The cortical parenchyma 
is very thin-walled and the cells large. . A thin-walled endodermis 
and pericambium surround two groups of leptome and two very 
narrow vessels in one diametrical plane. 
While studying the structure of the primary root of a number of 
specimens I noticed the same peculiarity as in Mitchella, that the 
lateral roots stay for some time enclosed within the cortex, which 
they traverse longitudinally; this peculiarity was noticed in several 
cases, but not frequently enough to make me believe that it is char- 
acteristic of this particular species. 
5 Dikotyla jordstammar. Acta Univ. Lund 19:18. 1882-83. 
