204 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The pericycle is much developed, and the pith much reduced ; and a 
cortex will be found, the cells of which are larger than those of the 
pericycle. The curious example of the bulbs formed by the leaves of 
Oxalis Deppei is then described, and also the case of Anemone coronaria, 
in which tubercles are formed by the swelling of the stem, root, and 
leaves. In the genus Allium also some of the flowers are frequently 
transformed into ovoid bulbils. 
The second part of the paper deals with physiological researches on 
tubercles, numerous experiments having been made to show the variation 
occurring in the proportion of water and of dry weight. 
The author concludes this portion by describing two methods 
employed to measure the temperature of tubercles. In the first method 
Thomson’s galvanometer was used, and the temperature noted, and in 
the second, specially constructed mercurial thermometers were employed, 
and the tubercles perforated in order to allow the bulbs of the thermo- 
meters to be introduced. 
As a summing-up, the following conclusions are drawn. Tubercles 
may be classified as follows according to their morphological nature : — 
(1) Tubercles formed by the stem, {a) With little or no secondary 
formation. (a) Dicotyledons (Stachys tuberifera, Oxalis crenata). 
(f3) Monocotyledons (Cyperus esculentus, Crocus vermis'), (h) With deve- 
lopment of secondary formations (Apios tuherosa, Epilohium Fleischeri). 
(2) Tubercles formed by the root, (a) With little or no secondary 
formation, (a) Dicotyledons (Itanunculus asiaticus, Ficaria ranun- 
culoides). (/?) Monocotyledons (^Asphodelus alhus, Simethis planifolia). 
(6) With development of secondary formation (^Spirsea Filipendula, 
Campanula harhata). (3) Tubercles formed by the stem and root 
[Aquilegia vulgaris. Beta vulgaris). (4) Tubercles formed by the leaves 
(Oxalis Deppei, Tulipa, Lilium). (5) Tubercles formed by the stem, 
leaves, and root (Anemone coronaria). (6) Tubercles formed by the 
flowers (Allium carinatum, Allium vineale, Notlioscordum fragrans). 
As to the chemical composition of tubercles, starch, inulin, saccharose, 
galactane, and glucose are the substances most frequently found in 
reserve. As a general rule it may be laid down that the temperature 
of tubercles is always higher than that of the soil which incloses them. 
The relation of the dry weight of tubercles to their fresh weight is very 
variable, not only according to the si3ecies, but even according to the 
period of development when the weight is taken. The proportional 
dry weight usually reaches a maximum coincident with the period of 
development when the tubercle is latent. 
Tubercles of Stachys tuberifera.* — M. L. Seignette states that the 
tubercles of Stachys tuberifera are formed by the swollen internodes of 
the underground stems. Their dimensions are variable, the longest 
observed being eight centimetres. The author then describes the 
formation of aerial stems on the tubercles, and also traces the develop- 
ment of the tubercles themselves. Their composition has been deter- 
mined by M. A. Planta, who states that they contain 75 per cent, of 
galactine, a carbohydrate intermediate between starch and sugar, and 
discovered by Schultze in lupin seeds. Various experiments having 
* Bull. Sue. Bot. France, xxxvi. (1889) pp. 189-91. 
