Scott. — On two new instances of Spinous Roots. 329 
tissues are reduced as compared with the lignified pro- 
senchyma. The spines themselves are shown by their 
structure to be rootlets, though highly modified. In them, 
as in the roots which bear them, the hardy woody portion 
is entirely stele, limited on the outside by the endodermis. 
The dry and withered cortex often forms a membranous 
envelope around the lower part of the spine. 
Histological details are reserved for a future communica- 
tion, which must await the opportunity for a study of the 
development. The spinous roots at present on the plant are 
not only mature, but to all appearance dead, serving no other 
than a purely defensive function. 
The normal roots have the structure usual among Mono- 
cotyledons ; it is of interest, however, to note that, when old, 
the rootlets die off, leaving behind a somewhat spiny base, 
so that there is here a certain approach to the peculiar 
character of the special protective organs. 
The plant has now been transferred to a hot, moist house, 
where it has rapidly formed a new twining stem, already 
nearly thirty feet in length and half an inch thick. The 
stem, which for some time remained unbranched, is clothed 
with strong, broad-based prickles, which bear a marked super- 
ficial resemblance to the spines on the roots. Anatomical 
examination, however, shows that the prickles contain no 
vascular elements, so that they are no doubt merely out- 
growths from the external tissues. 
At intervals averaging about fourteen inches, the stem 
bears thick, green cuspidate scale-leaves, two inches long, 
which are alternate near the base of the stem, but elsewhere 
are inserted in pairs. These curious organs, which are sessile, 
with a broad base, bear no resemblance to the normal foliage 
of the plant. They probably represent the modified and 
enlarged leaf-bases. The stem is now (April 27) producing 
branches from the axils of the scale-leaves, but at present 
the branches, like the main stem, bear scale-leaves only, and 
have as yet formed no normal foliage 1 . 
1 This has since appeared, on branches of the second order, May 5. 
