IDIOBLASTS. 



97 



KECEPTACLES FOR SECRETIONS. 



292. Individual cells (idioblasts) may differ greatly from their 

 neiglibors as respects tlieir contents. Sucli cells may be well 

 named after their characteristic contents ; as ciystal-cells, resin- 

 cells, raucilage-celis, tannin-cells, etc. 



293. They vary much in shape and size. Frequently they are 

 not readil3- distinguishable from their immediate neighbors by 

 anything except their contents. In other cases, however, they 

 may assume forms widely different from those of the cells around 

 them, and may also be distinguished bv their size. Tliej' are 

 often so associated togetlier as to form " glands." 



294. (Jrystal-celh. These sometimes, as de Bary points out, 

 curiously resemble the shape of the crystal or groups of crystals 



78 



■which they contain. Thus globular clusters are generally con- 

 tained in spherical cells, elongated prisms in elongated cells 

 (as in Quillaja). "In many trees each cambium-cell (as it 

 develops into a bast-fibre) maj- be divided by diagonal partitions 

 into numerous (20 to 30) chambers, the height of which is about 

 the same as the width, and each is filled hy a crystal or a small 

 cluster. In this case the general outline of the original cambium- 

 cell remains unaltered, and the whole row of compartments may 

 be isolated as a chambered fibre."* The bast-cells containing 

 crystals have been already noticed. 



295. Resin-cells. In a large number of plants soft viscid 

 substances are present, which exude when the tissues are 

 wounded. Thej' may be ronghlj- classed into (1) JBalsams, in 

 which resinous matter is mixed with a considerable proportion of 



1 De Bary : Vergleichende Anatomie, p. 145. 



Fig. 78. Crystal-cells : a, from the petiole of Begonia manicata; ft, a cell with raph- 

 ides, from Lemna trisulca; c, from Phallus caninus. (Kny.) 



