SECT. II. THE PULP. 817 



one another in all directions, sometimes interspersed 

 with small and granular, or bladder-like substances 

 occupying the interstices, and sometimes not ; but 

 of whose existence he began at last to be altogether 

 in doubt. His observations were chiefly made on 

 branches of the Lime-tree macerated in water. But 

 as the lon<? continued maceration to which the 

 branches were exposed, must have less or more dis- 

 organized the structure of the pulp contained in 

 them, he could not have inspected it in a perfect 

 state. 



Saussure investigated its structure in the leaves of Saussure, 

 the Bean and Periwinkle, in which he describes it 

 as composed of large and transparent fibres suc- 

 cessively inflated and contracted, and repeatedly 

 inosculating, so as to resemble strings of contiguous 

 vesicles forming a net-work. The contraction was 

 observed in the middle of the sides of the meshes, 

 and the inflation at the point of union.* 



One of the most distinct descriptions of this organ Compa- 

 that has yet been given is that of Comparetti, who rettl> 

 investigated its structure in the leaves of the Aloe, 

 Houseleek, and several other succulent plants, in 

 which it appeared to him to consist of an extremely 

 fine net-work interspersed with small and glandular 

 grains, enveloped in a green and glutinous sub- 

 stance and exhibiting an apparatus of vesicles. In 

 the leaf of Purslain the granules seemed to be ac- 

 companied with small and transparent hairs, and 

 * Obsorv. sur 1'Ecorce, p. 43. 



