THE ELEMENTARY TISSUES. 



, a kind of moss (Fig.10), it is of abeautiful red colour; these variations, 

 and especially in thickness, result from the 

 altered duties which it is required to perform. 

 Thus, in the structure of bark and fruits, it is 

 not merely thickened, but is lined by a deposit 

 of hard sedimentary matter, of great power 

 of resistance, in order to increase its strength 

 and to resist decomposition. This hardened 

 tissue is called sclerogen, or hard tissue (Fig. 9). 

 In less extreme cases the deposit is in much 

 smaller quantity, and appears only as minute 

 grains scattered over the surface. Such is 

 the case in the pith of the elder (Sambucus 

 niger Fig. 11). A yet more interesting in- 

 stance of this scattered mode of deposit is 



found in the hairs of the fornix (a part of the flower) of the Anchu&a 

 italica (Fig. 12). These are covered with a series of tubercles, which 

 are nothing more than isolated masses of a new deposit. In other 

 instances still, the thickening of the membrane appears to have been 

 produced by a deposit of the ordinary transparent organic mucus of 

 which it was originally composed, and still remains transparent, and 

 beyond this differs only from ordinary membrane in that this new 

 matter is laid on unequally, and certain transparent spaces are found 

 where the deposit has not taken place. These spots are oftentimes found arranged 



Fig. 9. Thick walled 

 cells of the Pinus Web- 

 biana, showing the 

 amount of deposit be- 

 tween the cavity a and 

 the outer cell wall. 



10. Fibres 

 of the Junger- 

 mannia crossing 

 each other spi- 

 rally, and, in 

 their natural 

 state, of a red 

 colour. 



Fig. 11. Pith of the ELDER (Sambucus 

 niger), showing the dotted tissue. 



Fig. 12. Tuber- 

 cles on the hair 

 of the fornix of 

 the Anchusa 

 Italica. 



Fig. 13. Section Fig. 14. Elementary 

 of the stem of fibre free from mem- 

 the VINE ( 7i- brane. 

 tis Vinifera], 

 showing the 

 vacant spaces 

 or dotted tissue 



with great "regularity, and sometimes in a spiral manner ; so that the tissue becomes 

 one of the most beautiful of vegetable microscopic objects. Such tissue is termed 

 " dotted" tissue, and is found in most plants, but more particularly in the common cane 

 (Rattan), and^he vine ( Vitis vinif era-Fig. 13). The use of this tissue is not well known. 

 Elementary Fibre (Fig. 14) is not formed from membrane, as though the latter 



