PROGRESS OF MICROSCOPICAL SCIENCE. 155 
embryo (near the suspensor), and the periblem increases to several 
layers on the sides of the embryo, but remains one-layered at both 
ends. As Hanstein has already shown, the root-cap and the primary 
bark are the result of these cell-divisions. Taking a more fully deve- 
loped embryo in which the cotyledons are present as two symmetrical 
projections, and rendering it transparent by Hanstein’s method, three 
membranes or layers of tissue are as clearly distinguishable in the 
cotyledons as in the axile portion of the embryo ; they appear as out- 
growths of the corresponding tissues of the axis of the embryo, and 
subsequently undergo the same changes. Briefly, says Famintzin, 
the principal results of my investigations may be thus expressed. 
‘In the earliest stages of the formation of the vegetable embryo three 
morphologically distinct layers of tissue appear, which during the © 
complete development of the embryo, and most likely during the whole 
life of the plant, retain, with few rare exceptions (the embryonic 
vesicle, for instance), their independence, and only certain defined 
tissues are formed from them. In other words, they correspond 
exactly to the embryonic membranes of the animal kingdom.’ ” 
Structure and Function of the Leaves of Dionea.—Two botanists 
have been lately engaged in studying these subjects, and their re- 
searches have been made perfectly independently of each other— 
M. Casimir de Candolle, in the ‘ Archives des Sciences Physiques et 
Naturelles, April 1876, and Dr. Fraustadt, in the first part of the 
second volume of Cohn’s ‘ Beitrige. As might be expected, in regard 
to the anatomy of the leaves they are in almost perfect accord, but in 
other respects their conclusions are somewhat different. De Can- 
dolle’s experiments extended over a period of only six weeks, and, in 
addition to the question of nutrition, he investigated the mechanism 
of the leaves. Briefly, his conclusions are these. Animal substances 
absorbed by the leaves are not directly utilized by the plant, nor 
necessary to its development. The marginal teeth and edge of the 
blade of the leaf form a member (organ) distinct from the rest of the 
leaf, which explains the reason why their movement is not simul- 
taneous with that of the valves of the blade. The stellate hairs and 
the glands are epidermal structures, whereas the excitable hairs on 
the surface of the valves are outgrowths of the fundamental tissue 
beneath the epidermis. The anatomical structure, as well as the 
development of the different parts of the leaf, favours the hypothesis 
that the movements of the two valves of the leaf depend upon variations 
in the turgescence of the parenchyma of the upper surface only of the 
leaf. According to both observers, no stomates are present on the 
upper surface of the leaf. Dr. Fraustadt’s investigations were of a 
somewhat different character. Without entering into them in detail, 
we may give the results of his experiments bearing upon the question 
of nutrition. The cells of the leaves of Dionza exhibit, in many 
respects, an unusual behaviour towards chemical reagents, which 
seems to point to the presence of a peculiar substance, the nature of 
which, however, nobody has yet succeeded in making out. Appa- 
rently it exists in the living cells in acid solution ; consequently it is 
precipitated by bases and redissolved by acids. Ammonia colours 
