92 
the cambium layer is but two or three rows of cellsin advance of 
the first row of ducts. 
On treating the newly formed wood-cells with Indol, fourteen 
rows gave the so-called reaction for lignine, the indications being 
principally confined to the lamelle joining the cells. In the most 
delicate tests for lignine with this reagent I find that in the older 
wood-cells the lamellz joining them give the most decided re- 
action; in fact, some woods, especially the bast fibres, give a re- 
action upon applying the proper acid before adding the Indol. 
In regard to the arrangement of the ducts in the completed 
annual growth, we see that as the wood-cells grow and the ring 
thickens, the ducts are inclined through the ring becoming 
smaller and smaller until in the outer portion in this wood they 
are but little larger than the ordinary wood-cells. This last fea- 
ture is only true of some of the Angiosperms; in others the 
ducts are practically the same size in all parts of the ring. 
Surrounding both the large and small ducts are series of small 
tracheids, their thin places being very small and delicate. Inter- 
spersed among the ordinary wood-fibres are cells which, in the 
alburnum, are filled with starch during a portion of the year. In 
some instances they are provided with septa, in others they ap- 
pear like round-ended cells one above the other. In transverse 
sections, these are seen to be arranged in irregular rows at right 
angles to the medullary rays, so that the wood is divided off into 
small rectangles of three to four rows of cells on a side surrounded 
by starch-carrying cells on all four sides. The function of these 
latter cells is not fully explained, but for a portion of the year 
they serve the purpose of storehouses for reserve material. In 
the specimen cut on the Ist of May the cells seem more densely 
packed than in any others that I have examined cut in the months 
from September to the present time. Later, when the tree has 
developed its leaves and flowered, I expect to find these cells 
nearly or quite empty. 
_. Wood of the White Oak cut on the same date had one row 
of ducts formed and many rows of wood-cells. The Hemlock 
had not formed any wood-cells. Branches taken on May gth 
from the Horse Chestnut, and also from Lilacs which were in full 
leaf and flower, had only traces of starch in the medullary rays. 
