408 Boewig on the Histology and 
tributed, each consisting of from five to ten angular cells 
with lignified walls. External to each protoxylem patch 
and sometimes adjacent to it, or at other times separated by 
what seems a fundamental tissue cell, is a patch of delicate, 
thin-walled protoplasmic cells which feebly show wall mark- 
ings in a few cells. 
Between each two of these bundles, about evenly dis- 
tributed, are two bundles of phloem which have no corre- 
sponding wood. These twelve phloem and four xylem 
patches are quite constant. Figs. 5, 6 and 7 show the dis- 
tribution of these into the roots. The wood patches break 
up into smaller groups, and there seems a possibility of the 
elements anastomosing before they run into the smaller 
roots. The wood elements show chiefly spiral markings. 
The roots have no root cap. They bear copious hairs, 
which are very turgid-looking, but quite short and mostly 
club-shaped. These extend to the very tip of the root. 
Sometimes the roots are ragged and broken off at the tip for 
want of aroot cap. They attain no great length, a seedling 
nine inches long (Fig. 4, d) having roots half an inch long, 
somewhat tenuous, pale, almost transparent-looking, and 
very thin and feeble in appearance. The side roots are 
much more vigorous usually than the tap root. The seed- 
ling pictured had a larger tap root than is usual. In the 
tap root, in fact, growth ceases early; it usually remains a 
mere cone, and never has the appearance of a useful member. 
6. Histology of Mature Plant.*—A mature stem in cross 
section shows externally a fairly well cutinized epidermis of 
rather square cells, which have dense contents and contain 
nuclei (8,1). Internal to this is a cortex (2) of four to six 
irregular layers, with intercellular spaces and which is dense 
with starch grains. The subepidermal layer is fairly regu- 
*Since my studies on this were completed, a paper has appeared 
by A. T. Schmidt (in Oesterr Bot. Zeitschrift, V. 52, 1902), which 
treats of the structure of the mature stem. 
