Ps 
Per 
PASSAGE OF FOOD FROM LEAVES TO STEM. 15 
a lateral direction is seen from the fact that, in a cross section, the 
coloured portion of the cambium extends on each side beyond 
the coloured portion of the phloem. The longitudinal sections 
show that the dye ascends in the cells of the cambium to the same 
height as it does in the phleem, but that the distance descended 
is greater. Transverse sections cut on a level with the point of 
insertion of the eosine show that the eosine travels along the 
medullary rays to the pith, but instead of entering the latter, it 
enters the vessels forming what is sometimes called the medullary 
sheath. The rhododendron stem showed this well, the medullary 
rays showing as thin red streaks, radiating from the pith to the 
phleem. To test or decide whether it were the case that the 
eosine, and therefore probably the food, enters vessels which are 
generally supposed to conduct water, eosine was inserted into 
several stems, and after some of it was absorbed the stems were 
placed in test tubes containing a solution of saffron. Both the 
transverse and longitudinal sections show the cortex and phloem 
stained red, the large vessels and the cells surrounding them 
yellow, while the vessels surrounding the pith are orange, showing 
that in these two latter the two currents had mingled. This result 
was particularly interesting, as the use of the two colours gives a 
vivid picture of the course followed by both the ascending and the 
descending currents—the eosine showing the course of the food 
from the leaves, and the saffron that of the water from the roots. 
From these experiments it is evident that eosine inserted into the 
cortical and bast tissue of stems travels by the phloem, medullary 
rays, and cambium, all of which consist of living cells. In one or 
two of the sections on the table you will notice that in one or two 
places the tissue next to the pith is very brightly coloured, showing 
that the stream has been directed towards these points. This 
seems curious, but in the stems which I examined I found that 
the increased flow was directed towards places where buds were 
developing. The section of box stem shows this clearly, but not 
so much so as when I sectioned it. Then, the outer tissue showed 
pure white, while the cells of the bud and those leading to it were 
turgid with eosine. This result was the more remarkable, for, as 
previously mentioned, when the eosine was inserted into the 
cortex of this stem none was absorbed. This coloration of the 
protoxylem was found in all the stems examined ; and as in the 
