Senecio precox, D. C., from Meaico. 37 
partitions of pith, have increased to such an extent as to form 
chambers one above another throughout the stem (Figs. 2a 
and 2b). Water is again absorbed, if the stem is immersed in 
that liquid, as I proved after the dry stem had been cut, so that 
the pith again swells up and assumes a_ nearly normal aspect. 
One remarkable exception, however, was found to the general 
dry appearance above described. At the very base of the stem, 
right at the cut off extremity, where one would least expect to 
find it, separated by two membrane-like diaphragms ed from 
the end LC, wasa single, watery, turgescent disc ¢d, as shown in 
the accompanying 
figure. The rea- 
son for the pres- 
ence of the single 
turgid disc was 
not hard to find. 
The proper con- 
duction of the 
water from the 
disc as from the 
other discs was 
prevented by the 
injury which the 
adjoining wood cells sustained, as indicated by their some- 
what dry and brown appearance (Text Fig. 25). 
From a long series of careful and painstaking experiments 
beginning with those of Hales in 1727, we know that water 
and other crude substances travel up through the alburnum of 
stems. The elaborated materials on the other hand are car- 
ried down through the phloem, or bast portion of the stem. 
In Senecio precox during the sixteen months that elapsed after 
the piece of stem was collected, the water was gradually baled 
out of the pith discs, or reservoirs, and was carried to the grow- 
ing point (Plate VIII, Figs. 1 and 2). The leaves in ordinary 
green plants lose daily large quantities of water by transpira- 
