AIR SPACES AND SECRETIONS. 75 



in most terrestrial plants they are small and angular. Air 

 spaces are of two kinds, schizogenous and lysigenous. The 

 former are formed by the splitting of the cell-wail common to 

 two or three cells. The latter result from the breaking down 

 of some cells, leaving a space. Secretion reservoirs or canals 

 and intercellular air spaces differ from each other only in their 

 contents, the former containing resins, gums, oleo-resins, etc., 

 the latter only air. 



INTERCELLULAR AIR SPACES AND RESIN SACS. 



CALAMUS (SWEET FLAG) RHIZOME. Make thin cross-sections 

 of the fresh rhizome or of the dried one after having soaked it 

 in water to soften it. Mount a section in water and examine 

 the outer third of the section. The parenchyma cells are loosely 

 arranged in chains with large and tolerably regular intercellular 

 air spaces. Most of the cells are filled with starch grains, 

 together with protoplasm and nucleus, but scattered here and 

 there among these are larger spherical cells filled with a 



Fig. 45. Part of cross-section of Calamus rhizome, a, volatile oil and resin sacs ; 

 b, sacs with transparent secretion ; c, starchy parenchyma cells ; d, air space 

 (Bastin). 



refractive or glistening material, sometimes intermixed with a 

 brownish solid. These are the secretion sacs (Fig. 45). The 

 refractive contents of the sacs are not saponified by caustic 

 potash, which fact indicates a volatile oil. 



Further evidence in favor of this conclusion is given by 

 applying cyanin solution to a section, when after some time the 

 contents are stained blue. The solid brown matter found in 

 some of the cells is resin and also stains blue with cyanin. 



