a?id Structure of its subterranean Leaves, 47 



Kot less wonderfully constructed and admirably adapted 

 for their situation and office are the imbricated scales, or 

 leaves, of the subterraneous stem, which, in size, shape, and 

 colour, very remarkably resemble the human teeth, and have 

 suggested its various names of Dentaria, Squamaria, and 

 toothwort. These have generally been considered as roots, 

 or scaly appendages to the roots ; but Mr. Bowman has 

 proved by numerous minute and delicate dissections under 

 the microscope, illustrated by a series of beautiful and highly 

 magnified drawings, and by a description and reasoning 

 which we regret our space will not allow us to follow through 

 all their details, that they are real leaves, adapted by their 

 peculiar organisation for their subterranean situation, where, 

 with the ordinary vessels of these organs, they could not 

 have performed their functions. We shall endeavour, with 

 the assistance of the drawings, to make this intelligible, after 

 giving the author's preliminary glance at the usual process 

 of vegetable life. " By laws which almost universally pre- 

 vail in the vegetable kingdom, plants imbibe moisture from 

 the soil by means of their radical fibres, and gases and 

 moisture from the atmosphere through the medium of pores 

 in the cuticle of their leaves. These elements are conveyed 

 into the parenchyma, where innumerable and inconceivably 

 delicate organs, stimulated by light and heat, throw off the 

 oxygen, and retain the hydrogen and carbon. These essen- 

 tial ingredients at once produce the green colour, and are 

 converted, by a mysterious and hidden process, into the 

 several substances of the vegetable body." The succulent 

 interior substance of the leaf of the Lathrae^a is pervaded 

 longitudinally by a number of parallel cavities or chambers, of 

 nearly its whole length, and whose sides are full of ridges 

 and hollows like the human ear. The entire inner surface 

 of these cells is thickly beset with innumerable papillae or 

 glands, each fixed on a pedicel, and so minute as not to be 

 discernible without a good microscope. A longitudinal sec- 

 tion of the leaf and one of its cavities is shown in the annexed 

 figure {Jig, 31.)j and a cross section ex- 

 hibiting all the cavities divided in the 

 middle, with their papillae, at^. 32., all 

 much magnified. The only opening into 

 the cells is between the involuted lower 

 portion of the leaf and the leafstalk, and 

 is so narrow and completely concealed as 

 to elude observation. It may, however, 

 be detected in a thin longitudinal section of the leaf, and is 

 seen inj%. 32. As the cuticle of the scales is not perfo- 



