Vegetable Physiology for the Year 1836. 445 



yellowish gum, which in the beginning fills the entire cell; subse- 

 quently however, it is generally deposited only round the bundle 

 of crystals, giving it a yellow colour. I could observe nothing, 

 however, of an intestinal canal-like organ, which these crystals 

 are said to contain*, and which is extended at full length, as it 

 were from aperture to aperture, in the interior of these cells ; 

 but they had the appearance common to other cells containing 

 such bundles of acicular crystals; only in this case thicker 

 and yellow partitions occur where these cells protrude into 

 the air-cavities. Besides the yellow gummy substance, there 

 often occurs a greater or less number of very small molecules 

 in these cells, arranged laterally from the bundle of crystals ; 

 and these also pass through the apertures of the cell when it 

 bursts by the entrance of water. This bursting of these cells 

 undoubtedly belongs to the most interesting observations for 

 which science is indebted to Turpin ; but to load these cells 

 with peculiar names would not be allowed on a general con- 

 sideration of the subject. In the diagonal sides of the air pas- 

 sages in Pontederia cordata, the occurrence of cells with spi- 

 cular crystals is quite of the same kind as those in the leaves 

 of the Aro'idece\ and we there also find similar single cells, 

 containing a yellowish gum-resinous substance; and indeed 

 sometimes with, but in general without crystals f. 



We are also indebted to Unger for an extended notice % on 

 the occurrence of carbonate of lime upon the surface of Saxi- 

 frage leaves. It has already been known for a long series of 

 years, that the gray and white efflorescence which occurs on 

 the upper surface of the leaves of various species of Saxifraga 

 consists of carbonate of lime ; this calcareous covering is espe- 

 cially found in great quantities on those very species of this 

 genus the leaves of which have at their borders small basin- 

 like depressions, as, for instance, Saxifraga Aizoon, S. ccesia, 

 mtacta, oppositifolia, &c. Unger explains this appearance of 

 lime on the leaves of the Saxifrage as an excretion ; and those 

 cavities which are filled with this excretion are regarded as 

 the excretory organs. " The epidermis of the leaves," says 

 Unger, " which otherwise consists of very thick-sided cells 

 with stripes and elevated points, becomes more delicate at the 

 place where they cover the secreting cavities ; and the cellular 

 tissue situated under these, a continuation of the fasciculi of 

 vessels (?), is also rather extended in length, and composed of 

 smaller cells which are never filled with vesicles of Chloro- 



*[...." einem darmartigen Organe, welches die Krystalle enthalten? he] 

 f Vide the figures on this subject in Meyen's Phytotomie, tab. v. 

 X On the influence of the soil on the diffusion of Plants, &c. Vienna, 



1836. p. 179- 



