208 The Air-vesicles of Bladderivorts. 



lower margin of its opening, which itself scarcely increased in 

 size, developed themselves much more than other parts ; so 

 that the complete utricle formed a small rounded body, laterally 

 compressed, prolonging itself on the upper surface or on one side 

 of the pedicel, and producing on the other side an opening in 

 the form of a funnel, projected into the interior of the utricle, 

 and having its exterior aperture closed by a fringe of hair 

 attached to the upper margin. The interior surface of the 

 funnel is adorned with differently shaped and elegant hairs, 

 disposed in regular order. All the interior surface of the 

 utricle is likewise covered with hairs composed of two cells, 

 each of which is prolonged into two appendages of unequal 

 length (Schleiden, loc. cit.). 



Benjamin explains the formation of these utricles by sup- 

 posing an arrest of development in certain segments of the 

 leaves ; instead of elongating themselves, they increase in 

 breadth; a constriction takes place, forming a narrow neck, 

 and they appear as little globular bodies, attached by a short 

 pedicel to the vein of the leaf. According to Benjamin, we 

 can follow these phases of formation by examination of a 

 single leaf from its base to its summit. The utricle, at first 

 filled with protoplasm, becomes, by the rapid absorption of 

 this fluid, a reservoir of air, and, stretching in all directions, 

 gradually assumes its ultimate form, which somewhat resembles 

 a stomach, the pedicel taking the place of the pylorus, and the 

 opening of the caudiac orifice. The mouth of the utricle he 

 represents as a valve opening inwards. . . . 



Schacht regards those organs of the Bladderworts, which 

 most botanists consider leaves, as leaf-bearing brandies, which, 

 in their young stages, are rolled up, like the fronds of ferns ; 

 under this crook, their leaves are formed in succession, and in 

 their axils small conical bodies appear, composed of little cells, 

 like the beo-mning of a bud. These small bodies soon exhibit 

 at their rounded extremities little cavities, produced by an 

 arrest of the development of their cells, the margins of which 

 grow, and the little cellular body, at first sessile, afterwards 

 exhibits a prolongation at its base in the form of a pedicel. 

 The lateral walls of the young utricle develop more and more, 

 and the air cavity becomes bigger, the margins of the lateral 

 walls incline towards each other, and fold inwards, while the 

 original aperture closes. The original opening is, in fact, a 

 valve, formed by a fold of the margin of the aperture; and 

 the beard which, according to Schleiden, closes the opening, 

 is found later on the external surface. . . . Thus Schacht con- 

 siders the utricles as modifications of the ramifications of the 

 axis, and not of the leaves. 



In April, 18G7, I studied the formation of the utricles of 



