934 Lee.- — Notes on the Anatomy and Morphology of 
towards the lower side of the protuberance to supply the leaf (/. t ., Text-fig. 4). 
As the trough continues up the protuberance it becomes more and more 
compact in structure, as the separate bundles gradually join up. Inside the 
trough run a few medullary bundles, whose xylem gradually decreases in 
amount as they continue upwards, until they enter the petiole. Their 
subsequent appearance and behaviour in the petiole will be described 
later. 
2. A cylinder of vascular tissue bending towards the upper side of the 
protuberance to supply the inflorescence ( i.c ., Text-fig. 4). In section this 
cylinder is seen as a ring bounded by an irregular line staining deeply with 
haematoxylin, representing crushed laticiferous cells, phloem, or both 
(Fig. 6). The parenchyma inside the ring is traversed by laticiferous 
vessels running in all directions, the majority appearing in transverse section. 
The vascular tissue consists of 
a ring of several groups of ex- 
ceedingly small tracheides just 
inside the deeply staining line 
(Fig- 7)5 surrounding and dis- 
tributed among which are small 
thin - walled cells resembling 
phloem. The inflorescence scar 
has round its margin a few 
minute spines ; in a longitudinal 
section of one of these, one 
tracheide was seen running up 
the middle, but this appears to 
be exceptional. From their 
position around the base of 
the inflorescence these spines 
The remaining medullary bundles run up between and beyond the ring 
bundles, and eventually separate into three portions which enter the three 
spines. 
(b) Structure of Spines. A transverse section of a young spine (Text- 
fig* 5 an d Fig* shows a small central cylinder of thin-walled tissue (Fig. 9), 
in which are five small groups of xylem (a, Fig. 9) arranged roughly in 
a ring, and similar groups of smaller cells resembling phloem in appearance 
(b, Fig. 9). There is very little pith. The greater part of the spine is com- 
posed of parenchymatous ground tissue, consisting of rounded cells, irregular 
in shape, with intercellular spaces between them. Towards the periphery 
the parenchyma of the ground tissue becomes thickened and lignified 
( L j Fig. 8). Outside this layer the cells are again thin-walled, smaller, and 
more compactly arranged, passing off into several layers of square water- 
Text-fig. 5. Diagram of transverse section 
across young spine. E = epidermis ; P = parenchyma ; 
w = water-storing region ; c = central tissue ; L = lig- 
nified tissue. 
are taken to be morphologically bracts. 
