S50 



ELEMENTARY ORGANS. 



CHAP. HI. 



plant ; and perhaps they are also somewhat pecu- 

 liar in their organization as may be inferred from the 

 following fact namely, that the white and milky 

 juice, with which they are filled in the stem and 

 branch of the Fig, does not ascend above the pedun- 

 cle. In the pith they are generally larger than in 

 any of the other parts of the plant ; and in plants 

 from which part of the trunk has been cut off, it has 

 been remarked that they become altogether larger 

 and more inflated than in plants of the same species 

 that have not been so treated ; which enlargement 

 is perhaps to be accounted for from the superabun- 

 dance of sap that now pervades them in consequence 

 of the diminished bulk of the vegetable. Senebier 

 speaks of other utricles distinct from those of the pa- 

 renchyma, by which he means the pulp or pith, but 

 without saying any thing explicit on the subject, and 

 without representing them as different in form.* 



Their dif- 

 ferent 

 sorts. 



SECTION II. 



Tubes. 



THE Tubes are the vessels formed by the cavitios 

 of the longitudinal fibres, whether as occurring in 

 the stem of herbaceous plants, or in the foot-stalk 

 of the leaf and flower, or in the composition of the 

 cortical and ligneous layers, or by longitudinal open- 

 ings pervading the pulp itself, as in the case of the 



* Phys. Veger. vol. i. p. 100. 

 2 



