200 I.ETTER XL VI. 



the table of the microscope, in water, and illumi- 

 nated it bv lioht thro\Mi from below, first remark the 

 structure of the bark ; it is a thick, firm layer of hex- 

 agonal cells, part of which (A. f. — g.) are arranged 

 in one way, and part (A. e.— /'.) in another, so that 

 a strip of the bark might without much difficulty, be 

 split into two plates. Among the green cells of the 

 bark, vou will remark a few round white points : these 

 are the mouths of fine, spiral-coated tubes, or spiral 

 vessels. Between the bark and the wood is a thick 

 layer (A. d. — e.) of exceedingly delicate, thin, green 

 cells, in which you may discern the round mouths of 

 other tubes of various sizes ; these are other spiral 

 vessels of very large size, and in such abundance, that 

 thev look hke a stratum of tow, between the wood and 

 bark ; each of these large spiral vessels is formed of 

 four threads, twisted spirally. Next the spiral struc- 

 ture comes the wood, the outside of which (A. c. — d.) 

 is hard, compact, and homogeneous, and then becomes, 

 towards the centre (A. b. — c), more open, with a 

 quantity of unequal, round, or oval perforations, .which 

 are also the mouths of large spiral vessels ; finally, 

 you come to the pith (A. a. — h.), consisting of thin- 

 sided, large cells, in which are more mouths of vessels. 

 All this is highly curious, and shews you what an 

 infinite multitude of forces, represented by these little 

 organs, are required to maintain the life of Nepenthes. 

 You will not, however, form a correct notion of 

 their real nature, unless you also examine a longitu- 

 dinal slice of the same part of the stem {Plate 

 XLVII. B.) ; hitherto you have only seen the ends 



