KINGSLEY: SPLITTING OF RHIZOME OF DELPHINIUM 313 
tion, from the excessive amount and comparative protection of 
the parts thus clothed. Part of its bulk must of necessity arise 
from the necrotic parenchymatous pith and primary bundles cut 
off in the center. And careful examination of the dead elements 
found here, shows ducts, spiral and reticulate, as well as many 
fibrous pieces made up of stereome strands. 
Jost believes that each old year’s wood, as it becomes useless 
for water conduction or ceases to be in direct connection with the 
present year’s annual growth, is cut off from the living functioning 
parts by this circular periderm formation, and dies, thus adding 
to the bulk of necrotic tissue and lessening the area of activity. 
Jost describes minutely this phenomenon in several cases. In 
Gentiana cruciata,* as secondary growth continues, forming new 
wood and cortex, old tissues are constantly cut off by an ever 
originating parenchymatous periderm and the significance of this 
periderm is to separate the functionless wood and bast in the 
rhizome and root from the living. In Corydalis Ochroleuca,} only 
those bundles are kept that are in direct union with leaf parts. The 
rest die off, and jagged parenchyma strands in the wood, by turning 
brown and dying, form the splits. In Aconitum Lycoctonumt 
(as in Gentiana) under symmetrical cork formation about the 
living tissues, and with parenchyma cells cut off that become corky 
about dying tissues, never more than two years’ growth is left 
active. Periderms formed later are either concentric with the 
first or contribute to further splitting as already described. In 
Sedum,§ old years are all cut off by the periderm, and only the one 
youngest ring remains active. In Delphinium, such whole- 
sale destruction apparently does not exist. No necrosis, cutting 
off bundle elements, can be found before the second year, and in 
no older form is less than two years’ growth active. 
In a rhizome showing four years of xylem (FIG. 6) the primary 
xylem is disintegrated, in the center directly outside of the necrotic 
pith region, and is cut off from all the rest of the wood by heavy 
cork zones that have particularly strong inner rims, and surround 
each a different one of the five columns of the split rhizome. Each 
* Jost. Loc. cit. pp. 444, 461. 
+ Jost: . Loc. cit. pi 477. 
TJost. Loc. cit. p. 490. 
§Jost. Loc. cit. p. 504. 
