CHAP. I. CELLULAR TISSUE. 11 



is found in the pith of all plants ; and the rice paper, sold in 

 the shops for making artificial flowers, and for drawing upon, 

 which is really the pith of a Chinese plant, is an excellent 

 illustration of it. If the force of extension or compression be 

 greater in one direction than another, an endless variety of 

 forms is produced, of which the following are the most worth 

 noticing : — 



1. The oblong ; in the stem of Orchis latifolia, and in the 

 inside of many leaves. (Plate I. fig. 9.) 



2. Tlie lobecl (Plate I. fig. 2.y); in the inside of the leaf of 

 Nuphar luteum, Lilium candidum, Vicia Faba, &c. : in this 

 form of cellular tissue the vesicles are sometmies oblong with 

 a sort of leg or projecting lobe towards one end ; and some- 

 times irregularly triangular, with the sides pressed in and the 

 angles truncated. They are well represented in the plates of 

 Adolphe B]"ongniart's memoir upon the organisation of Leaves, 

 in the Annates des Sciences, vol. xxi. 



3. The square; in the cuticle of some leaves, in the bark of 

 many herbaceous plants, and frequently in pith. (Plate I. 



fig- 13.) 



4. The pj'ismatical ; in some pith, in liber, and in the vici- 

 nity of vessels of any sort. (Plate I. fig. 6.) 



5. The cylindrical (Plate I. fig. 8. a); in Chara; this has 

 been seen by Amici so large, that a single bladder measured 

 four inches in length and one third of a line in diameter. 

 (Ann. des Sciences, vol. ii. p. 246.) 



6. The fusiform or the oblong pointed at each end; in 

 wood, and in the membrane that surrounds the seed of a 

 Gourd. These are what Dutrochet calls clostres. (Plate II. 

 fig. 19. 8.; Plate I. fig. 5.) 



7. The muriform; in the medullary rays. Tliis consists of 

 prismatical bladders compressed between woody fibre or 

 vessels, with their principal diameter horizontal, and in the 

 direction of the radii of the stem. It is so arranged that 

 when viewed laterally it resembles the bricks in a wall; 

 whence its name. (Plate I. fig. 7.) 



8. The compressed; in the cuticle of all plants. Here the 

 bladders are often so compressed as to appear to be only a 



