KINGSLEY: SPLITTING OF RHIZOME OF DELPHINIUM 311 
single-layered epidermis. Jost mentions the fact that ‘the aerial 
stems of so many Ranunculaceae show only a slight growth in 
thickness and develop no interfascicular cambium.’’* Farther 
down we find a complete cambium ring, through the activity 
of which the radial length of the primary bundles has been in- 
creased, not so much in xylem and phloem elements as in paren- 
chyma, 4-7 rows of which are found on each side of the cambium. 
This has pushed the stereome cap farther out in the cortex, and 
we also find a periderm beginning to form to replace the epidermis. 
The secondary thickening in this and later sections is formed by 
a cambium that produces one ring of elements annually. This is 
anomalous to some extent, since it forms much more parenchyma 
than sieve or xylem ducts. The reason for this fact cannot be 
absolutely proved, but there may be a water storage function for 
all these thin-walled cells, which a xerophyte might very readily 
utilize. The cambium (FIG. 4) next produces weak secondary 
xylem elements outside of the primary xylem (which is flanked 
on both sides by stereome), followed by about five rows of 
equilateral parenchyma cells and five rows of brickshaped cells. 
The general change in shape suggests the spring and fall cells in 
wood, and probably owes its existence to the same slowing down 
in growth at the end of the growing season. 
Outside of the cambium much parenchyma and a few sieve cells 
have been produced. In the outer cells of this closely packed cortex, 
separating it from the loose, irregular peripheral cells, appears 
a single row of cells with slightly thickened lateral walls, which 
makes a complete circle of the stem and forms an endodermis. 
Some of the primary cortex with its masses of stereome has become 
broken up, probably due in part to growth pressure from within. 
There is a darkening of the pith around the hollow center, which 
indicates necrosis of the tissues. In the next lower section (FIG. 5), 
which shows three years growth in thickness, we find the paren- 
chyma which surrounds the first year xylem assuming the irregular 
appearance of the cortical parenchyma. A circle of cells exactly 
similar to the endodermis has formed inside, cutting off from the 
rest of the wood the xylem of the original bundles, enclosing the 
* Jost. Die Zerkliiftungen einiger Rhizome und Wurseln. Bot. Zeit. 48: a8. 
JI 1890. ae Aconitum Lycoctonum.) 
