50 THE INTERNAL 



particularly in trees, bark becomes developed from it, which 

 in some trees (for example, in the Cork-oak, Quercus 

 suber) is very soft and elastic and, as cork, is applied to a 

 number of purposes. The vascular bundles are important 

 on account of the substance of their cell- walls constituting 

 wood and woody-fibre or bass. The remaining tissue, the 

 cellular, is chiefly useful on account of the contents of the 

 cells. 



Of all the forms of cells, the wood and bass-cells are 

 undoubtedly the most important in the domestic economy 

 of mankind. The different kinds of wood may be easily 

 distinguished by the microscope, even in the most minute 

 fragments ; the distinction of the most consequence, is 

 that between the peculiar wood of the Fir and Pine tribe 

 and that of all other trees, and this is perceptible even in 

 petrified wood (PI. n. Figs. 8, 9, 10). The " bass-cells" 

 are the longest of all ; their walls are generally very thick 

 and mostly much bent (PL i. Fig. 8), but very rarely 

 marked with pores or spiral fibres ; only in the silk-plant 

 (Asclepias Syriaca), the Oleander and allied plants is a 

 spiral striation of the walls observed. No other bass-cells 

 are easily distinguishable by the microscope, however 

 different may be the plants from which they have been 

 taken. The bass-cells, however, on account of their length 

 and curvature, supply almost the sole material of our woven 

 fabrics and cordage. As I have already observed, plants 

 of the most different kinds are used for these purposes. 

 Among us, flax and hemp are the staple ; in the Philippine 

 Isles, the bass from the leaves of a species of Plantain ; in 

 Mexico the leaves of some wild species of Pine-apple furnish 

 a similar substance. The New Zealand flax has recently 

 become of some importance for naval purposes ; this is 

 obtained from the leaves of a Liliaceous vegetable. Peculiar 



