170 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Arum and Iris , and the conns of Colchicum and Ranunculus , the reserves 
are formed almost exclusively of starch, with small quantities of dextrin 
and sugar. In the tubers of Ophrys and the bulbs of Lilium , Tulipa , 
and Hyacinthus, starch is associated with dextrins; in the corms of 
Ficaria , with dextrin and non-reducing sugars. In the tubers of 
Dahlia we find inulin and levulin ; in the tubers of the artichoke, 
inulin, levulin, and non-reducing sugars ; in the bulbs of Allium and 
Aspliodelus, chiefly reducing and non-reducing sugars. 
The digestion of the carbohydrates is a very uniform process. 
Starch is transformed into dextrin, then into non-reducing sugars, then 
into reducing sugars. With inulin, the process is the same as with 
starch, but levulin takes the place of dextrin, and the last term is not 
glucose but levulose. Stachys tuberifera is exceptional in forming 
galactan, a substance intermediate between dextrin and sugar. In all 
cases the digestion of the carbohydrates is due to the action of a 
diastase. 
In the formation of the carbohydrates, the processes are, as a rule, 
the inverse of those which take place in their digestion. 
In biennials, the reserves are formed during the first, digested during 
the second year, with an intermediate period of rest. In perennial 
organs (rhizomes of Iris and Arum, tubers of Dahlia, &c.) the amount 
of reserve-materials reaches its maximum at the commencement, its 
minimum at the end of each period of vital activity. During each 
period of repose active internal transformations are going on, due to 
the action of the diastases formed from the protoplasm. 
(3) Structure of Tissues. 
Transformation of Alburnum into Duramen in the Oak.* — M. E. 
Mer has studied the mode of formation of the duramen out of alburnum 
in Quercus Robur and pedunculata. The duramen is characterised by 
a resorption of the starch in the ligneous and radial cells ; by the 
appearance in these elements of a large quantity of tannin ; by the pro- 
duction of thyllas in the large vessels ; and by the impregnation of 
tannin into the walls of all the elements, especially those of the vascular 
bundles. It was determined by observation and experiment that the 
entire disappearance of starch from the cortical region is not due to 
migration but to resorption, it being replaced by fresh starch which is 
being constantly formed in the leaves. The appearance of tannin coin- 
cides with the disappearance of the starch. The formation of thyllae 
in the duramen is due to a renewal of cellular activity produced by 
hypernutrition. The main function of the alburnum is therefore to 
furnish a supply of nutriment for the production of the “ perfect wood ” 
(duramen). 
Floral Fibrovascular System of the Bicarpellary Gamopetalse.f — 
M. P. Grelot has studied the course of the vascular bundles in the flower 
of a large number of genera belonging to the bicarpellary Gamopetalas 
(Gentianales, Polemoniales, Personales, Lamiales), and has come to the 
following general conclusions. The vascular bundles of the leaves, 
* Ann. Sci. Nat. (Bot.), v. 1897 (1898) pp. 339-77. Cf. this Journal, 1896, p. 323. 
f Tom. cit., pp. 1-151 (8 pis.). 
