30 = Harshberger—Water Storage and Conduction in 
A question which very naturally arises in studying this plant 
is: How is the water prevented from being lost at the surface ? 
The answer is found in the structure of the cortex. The bark 
consists of tabular cells arranged in a number of layers out- 
side of the cortex proper, which is green to a considerable 
depth. Prominent in the cortex are reservoirs filled with a 
balsam-like fluid which hardens upon exposure to the air. 
These balsam receptacles are found in two positions in the cor- 
tex, under, near the phelloderm, in the exocortex, and next 
the bast in the endocortex. When a section is cut, the liquid 
exudes, hardens and thus closes the wound. Aeration of the 
stem is accomplished by the lenticels. 
Upon a priori grounds, the pith stores up water in Senecio 
precox during the rainy season for the use of the plant during 
the dry period, when the flowers shoot forth and the seed is 
produced at the expense of the reserve water. Have we evi- 
dence that such is the procedure ? 
Fortunately, a fully developed stem (Plate VII, Fig. 3) was 
collected on August 27, 1896, on the Pedregal near Tlalpam. 
It was carried to Philadelphia in a trunk and _ laid aside in the 
dry state for a number of months. Upon examination, it was 
found to have sprouted. Short lateral branches with unde- 
veloped leaves soon appeared, and for the last sixteen months 
without water or soil, the growth has gone on, until at this 
writing, December 24, 1897, the dry stem shows at least four 
green branches (Plate VII, Fig. 3; Plate VIII, Fig. 2a), tur- 
gescent and tipped by a number of small green leaves. These 
four branches measure respectively 1%, 114, I, 34 inches. 
Sections of this dry stem show the cortex region to be 
practically as turgescent as when first collected, the balsam 
exuding when a sectionis cut. The wood, too, appears normal 
in color and somewhat moist to the touch. The pith, how- 
ever, is dry ; the water has been removed from the discs, which 
are dry, paper-like and extremely brittle (Plate VIII, Figs. 2a 
and 2b). The spaces between the successive discs, or lamellar 
