546 Reed .— On the Anatomy of some Tubers. 
xylem parenchyma, together with parenchyma derived from the division of 
the interfascicular cambium. The cortex is not concerned with the addition 
of any appreciable amount of tissue to the tuber. 
Tubers of the White and Red Fir Apple Potato (Sutton and Sons, 
Reading) were also examined. These tubers more nearly resemble ordinary 
stem structures in their external characters than does either of the two 
tubers already described. Their anatomical structure corresponds with 
their external appearance and more nearly approximates to that of a 
normal stem. 
As in S', tuberosum the tissues concerned with tuberization are the pith 
and to a certain extent the cortex, together with the parenchyma which 
separates the medullary phloem from the protoxylem. The development 
of tuberization parenchyma, however, does not go on to such an extent as 
in any way to render obscure the normal stem structure, so that on the 
whole we may say that it represents what we have in the case of S. tuberosum , 
only it does not go quite so far with its tuberization, particularly with 
respect to the formation of parenchyma from the tissue separating the 
medullary phloem from the xylem. 
Summary of Results. 
1. The tuber of Solarium tuberosum is formed mainly from medullary 
parenchyma and from the parenchyma between the xylem and the medul¬ 
lary phloem. This latter source is largely responsible for the scattered 
distribution of the medullary phloem strands in the tuber. 
2. The medullary phloem probably serves as the channel for supplying 
food material to the parenchymatous portion of the tuber. 
3. The tuber is covered with a layer of cork which is developed from 
the hypoderma. 
4. The structure of the tubers of the White and Red Fir Apple Potatoes 
is similar to that of .S', tuberosum , but much less tuberous tissue is developed. 
5. The tuber of Helianthus tuberosus is made up of medullary paren¬ 
chyma, xylem and medullary ray parenchyma. In this latter respect it 
differs from S. tuberosum . 
6. The distribution of inulin appears to have some influence on the 
meristematic activity of the cells. 
7. In tubers of 5 . tuberosum and H. tuberosus few, if any, secondary 
lignified elements are formed. 
In conclusion I wish to express my thanks to Prof. J. B. Farmer, F.R.S., 
for the suggestion that this work should be undertaken, and for his help and 
advice during the progress of this research ; and also to Mr. Hales, the 
Curator of the Chelsea Physic Garden, where this work was carried out. 
