178 , Fhilofnatlc Soclety-^Boidny, 



not to Ibf ir iife, which is uncertain^ He firft examines' tlieii 

 efTeiitial nature, and then follows their variations in the dif- 

 ferent parts and different clalTes of vegetables, and under va- 

 rious circuniftances. From thefe fads he endeavours to de- 

 termine their ufe. 



The cortical pores form part of the cortical tiflue of the 

 leaves. , It may be feen by the niicrofcope that they arc oval, 

 and furrdunded by an oval border, which connefts them, by 

 two or three fibres, to the rett of the tiflue. The meflies of 

 the'tiflUe are mpre lengthened, and always ^without pores on 

 the fibres; the bridles, on the other hand, are always placed 

 on the fibres of raniificutions. DecandoUe is of opinion that 

 thefe. qdrtic^^l ,pores are placed at the extremity of the fibres 

 which compofe the leaf. This idea was fuggefted to liim by 

 the conformation of. the criijjhlay. la^lea^ cotyledons^ &c. h 

 ^ bundle, of fibtres traverfes tjie'parencihynia.of their leaves, and 

 ends at the bark ; the plaqe where it ends is an aflemblage of 

 pores, whereas fcarcely any are found on the rell of the fur- 

 face. This idea is confirmed by the pores being very nume- 

 rous on coriaccou? leaves, ;ind^very little fo on thofe that are 

 pulpy, which have more juice and fewer fibres. 



The cortical pores are found in particular on the leaves. 

 The leaves of herbs, in general, have fome of them on both 

 faces, and thofe of trees on the lower furface only ; which 

 coincides with the experiments of Bonnet on fu^lion. The 

 flems have no pores, except thofe of plants which are very" 

 herbaceous ; fuch as the cucurhita^, graffes, and thofe which 

 ■are deftitute of leaves, as the caitus^ epbedruy 8cc. The roots 

 •never have pores. Some are found on the ftipulae, and the 

 foliaceous and durable bra^lece. The calices in general are 

 furnillied with them ; but^ on the other liand, the corollge 

 have none : ihis rule, hpweve.r, is liable to fome exceptions, 

 u liich DecandoUe propofes to explain in a particular me- 

 njoir. The pulpy pericarpia are unprovided with pores, but 

 thofe vi'hich are coriaceous have tliem. -The fkins of feeds 

 have none, but they are found on the feminal leaves. None 

 of them, however, are found on the cotyledons which re- 

 main on the ground, nor on thofe of French beans. 

 '. If the bark of various families be examined, it will be 

 : 8 . found. 



