539 
Reed.—On the Anatomy of some Tubers. 
Whilst he does not deal particularly with the origin of the tuberous tissue, 
his figures suggest that it is formed from wood parenchyma of the secondary 
hadrome or wood. It is worth noticing that although these tubers are the 
principal means of propagation of this plant, neither the tuberous tissue nor 
the cortex contains any starch, and other deposits appear to be scarce. The 
cortex also appears to contribute some part of the tuberous tissue. 
F. J. F. Shaw (11) describes the anatomy of the tuberous seedlings of 
Araucaria Bidwillii , but he gives us no account of how the tuberous tissue 
arises. 
Anatomy of Tubers of Solanum tuberosum. 
The tubers of S', tuberosum arise as terminal swellings on long under¬ 
ground stems or stolons. These stems arise in the axils of the lower leaves 
of the main shoot and grow more or less horizontally outwards, and sooner 
or later they swell up at their tips to form tubers. That these structures 
are stems is shown by their origin and their anatomical and morphological 
structure. 
The plants used in this investigation were grown in soil, and at various 
stages of their development tubers were cut off and preserved in alcohol. 
To determine the course of the vascular bundles in the tuber, series of 
transverse sections were cut by hand from the stolon to the tip of the tuber. 
The stolon presents a typical stem structure. There is a ring of bun¬ 
dles consisting of four larger groups of xylem elements with a few smaller 
groups scattered between them ; each group is accompanied on its outer 
side by a group of phloem elements. Each bundle is also accompanied on its 
inner or medullary side by a group of phloem elements, so that the structure 
of the bundles is bicollateral, a structure which appears to be quite typical 
for the Solanaceae (4). The vascular cylinder is surrounded by an easily 
recognized endodermis (PI. XLII, Fig. i, En.). It is worthy of notice that 
this endodermis is entirely devoid of starch grains. This appears remarkable 
when one is reminded that the cortex and pith contain very abundant quan¬ 
tities of starch grains. This absence of starch from the endodermis of the 
stolon of S'. tuberosum is remarkable in that in most plants the endodermis 
is the tissue which almost invariably contains starch. It may possibly be 
explained that the absence of starch is due to the fact that the whole of the 
protoplasm of the endodermal cells is used up in their formation, for Millon’s 
test and the xanthoproteic reaction failed to reveal the presence of proto¬ 
plasm. Since then all the protoplasm is apparently used up in the formation 
of the cells, in their adult stage they would be incapable of any further 
activity. 
The endodermis is surrounded by about eight or ten layers of paren¬ 
chymatous cortical cells. These parenchymatous cells of the cortex contain 
abundant starch grains and protoplasm, and usually a nucleus as well. The 
O o 
