422 Foreign and Miscellaneous Intelligence. 



stomata. It is into these cavities in the cavernous parenchyma of 

 aerial leaves that the atmospheric air penetrates when it is absorbed 

 by the surface of the utricles of the parenchyma, that are distended 

 with the fluids which seem to nourish the plant. 



According to M. Brongniart, aquatic leaves, if submerged, differ, 

 in being completely destitute of epidermis. It is not alone stomata 

 that they want, as has long been known, but the epidermis also. 

 There are none of the cavities that abound in the parenchyma of 

 aerial leaves, but, on the contrary, the cellules of the tissue are com- 

 pactly fastened together without any interstice, and the air dissolved 

 in the water can only act on their outer surface. For this reason the 

 proportion borne by this surface to the whole mass of the leaf is 

 unusually great ; the leaves, from want of epidermis, dry up quickly 

 when exposed to the air, and can only exist in water or a very 

 humid atmosphere. 



Hence the author concludes that the epidermis is destined to pro- 

 tect aerial leaves against too rapid evaporation, and the stomata or 

 pores of this epidermis become necessary to maintain a communica- 

 tion between the atmosphere and the parenchyma. 



9. CRYSTALS OF OXALADE OF LIME IN PLANTS. 



M. Turpin has discovered that the cellules of Cereus Peruvianus con- 

 tain an immense quantity of crystals of oxalate of lime. He represents 

 them as appearing to the naked eye like very fine glittering sand, 

 and, under the microscope, as rectangular prisms, with tetraedral 

 points and a square or parallelogrammic base : their size is variable ; 

 they are sometimes found collected in groups of three and four, but 

 more commonly forming radiating spheroidal clusters, composed of 

 crystals of various sizes. They existed in such abundance in some 

 parts of the tissue as to form at least an 80th of the whole mass. 

 The presence of such crystals in the tissue of plants has lately 

 become well known to botanists, and are distinguished by the name 

 of raphides. They may be found abundantly, in the form of needles, 

 in the common Hyacinth, and in most succulent Monocotyledons, 

 and in Phytolana decandria they give a kind of silvery appearance 

 to the subcuticular tissue ; but in no plants had they been previously 

 seen so abundant or so large as in the plant which forms the subject 

 of M. Turpin's memoir. 



10. GROWTH OF VEGETABLES. 



There is no subject in vegetable physiology more obscure than 

 the manner in which plants increase in size. While botanists 

 are at issue as to such a point as the origin of the wood and 

 the bark of dicotyledonous trees, it is scarcely to be expected that 

 they should agree upon the mode in which development is effected. 

 In truth, nothing whatever certain is known upon the subject. 



