444 Prof. Meyen's Report of the Progress of 



serving that in these cases also the crystals, occurring singly* 

 are surrounded with a cellular membrane. 



Turpin* has made an interesting discovery with reference 

 to the occurrence of acicular crystals in the tissue of the 

 Aroidece. It is true that long ago it was known that these 

 crystals, as well as entire druses of small crystals, occurred in 

 the cells of the Aroidece ; but in the leaves of Caladium escu- 

 lefitum, these spicular or needle-form crystals, which here, a.v 

 in all other cases, always occur in the form of fascicles, are 

 not only very long and of extreme tenuity, but the cells also 

 in which they are found differ in many respects from the other 

 cells of the leaves of this plant. These crystalliferous cells 

 are those which Turpin has named Biforines; and, for reasons 

 which will now be stated, the position of these long crystal- 

 liferous cells in the leaves of the plant above-mentioned was 

 not perceived by Turpin ; and it is this very circumstance 

 which, in some respects, assists in explaining this discovery 

 which Turpin has made with regard to them. These cells are 

 several times larger than the surrounding ones of the diachyma 

 of the leaves of Caladium, which are filled with green-coloured 

 cellular sap-globules; and they are so placed that their middle 

 parts only lie between the cells of the partitions which separate 

 from each other the air-passages, with which these leaves imme* 

 diately below the epidermis are filled ; they protrude, there- 

 fore, with one end into one air-cavity, with the other end into 

 the neighbouring air-cavity. The membrane forming these 

 cells is considerably thicker than the surrounding green cells 

 of diachyma; they also exhibit a brownish yellow colouring. 

 If we now immerse these cells with their bundles of crystals 

 in water, most of them open at both ends, and the crystals 

 gradually more or less rapidly come out at the apertures, 

 either through one aperture, generally, however, through both. 

 Turpin has figured these apertures of the cells with excessive 

 regularity, so that one would imagine that he perceived some 

 entirely peculiar formation in these cells; however, even with 

 the highest magnifying powers, I have never been able to ob- 

 serve these apertures trimmed thus regular, and, as it were, 

 edged with broad borders; but the drawing which Turpin has 

 given, (rig. 4. pi. iv.), as regards the structure of the ends of 

 these cells, before their bursting, I find to be drawn quite 

 after nature. The cause of the bursting of these crystal- 

 liferous cells exists in the hygrometrical condition of the sub- 

 stance which occurs with the crystals in these cells; it is a 



* Observations sur les Biforines, organes nonveaux situes entre les vesicules 

 du Ussu cclhdairc des feuiltes dans un certain iwmbre d'especes vegetates ap. 

 jpartcnant dlafamiUe des'Aroidecs. — Ann. des Sciences, Nat, 1836. ii. p. 4, 27. 



