538 Reed.—On the Anatomy of some Tubers. 
manured with dung which was contaminated with Fusarium ; in the second 
lot the infection was irrdguli&e et tardive . Since he obtains a greater yield 
of tubers from the first lot than he does from the second, the inference is 
drawn that the infection by Fusarium is responsible for the difference in 
yield. Bernard appears to have overlooked the fact that the manuring of 
the soil of the first lot of tubers would probably account for very consider¬ 
able differences between the harvests of the two lots. This probability is 
strengthened in view of the work of L. Dufour (6), who has shown that 
plants of S'. Commersonii are very susceptible to changes in the physical and 
chemical condition of the soil. Dufour concludes that moist earth favours 
the production of tubers, and that sandy soil is more favourable to their 
formation than is sandy soil mixed with varying percentages of calcium. 
None of these authors has given us any account of the anatomical 
structure of the potato, and very few accounts of the anatomy of other 
tubers are available. 
E. Bucherer (2) has dealt with the anatomy of several tubers of 
Dioscoreaceae, but he deals more particularly with the origin of the tuber 
and the features of its vascular anatomy, and he makes no reference to the 
tissues which are concerned with the formation of the tuberous tissue. 
A. De Bary (4), dealing with the tubers of Dioscoreaceae, states that 
in those tubers which exhibit secondary thickening the origin of the cambium 
is unknown. In the specimens investigated, however, a cambium surrounds 
the whole lateral surface of the tuber inside the cortex. This cambium 
gives rise to interfascicular tissue consisting of thin-walled parenchyma which 
forms the main mass of the tuber. 
Leclerc du Sablon (10) also deals with the tuber of a member of the 
Dioscoreaceae, Tamus communis. He deals more particularly with its 
development and morphological nature than with its anatomy or the origin 
of the tuberous tissue, and his figures give us no clue as to the tissue which 
is responsible for forming the main mass of the tuber. 
Miss E. Dale (3), dealing with the tuber of Dioscorea sativa , mentions 
that it is made up of parenchymatous tissue, but does not discuss its origin. 
Marcel Dubard and Rene Viguier (5) give an interesting account 
of the tuber of Euphorbia Intisy. This is a root tuber. The root shows 
a central cylinder consisting of a hexarch stele. Secondary thickening com¬ 
mences in the usual way by a cambium which surrounds the xylem portions 
of the vascular cylinder. This cambium, however, forms few secondary 
xylem elements, but gives rise to long radial rows of parenchyma cells which 
compose the bulk of the tuber. At infrequent intervals a few wood elements 
may be formed, but owing to the very extensive development of parenchyma 
these become cut off as ‘ ilots vasculaires ’. The pith also contributes to the 
tuberous tissue. 
Theo. Holm (7) gives an account of the root tubers of Rhexia virginica. 
