124 PLANT ORGANS OR PARTS OF PLANTS. 



reticulated tracheid-like construction characteristic of 

 many of the ferns. The tracheids are much of the same 

 character, varying only in the complexity of their mark- 

 ings and in their diameters. Some of the tissue of the 

 phloem may, be seen. This consists of elongated and very 

 delicate thin -walled cells, which are much crushed and 

 contorted in the powdering. Characteristic features of 

 this rhizome are the glandular structures. These are 

 found in the parenchymatic tissues, or, more frequently, 

 broken into small fragments and free ; when perfect they 

 consist of small dark-brown sacs, filled with resin, and 

 averaging 25 to 40 microns in diameter; a minute stalk 

 may sometimes be noted. If the rhizome is particularly 

 old and much stipe tissue included in the powder, typical 

 bast fibres may be found. 



Chemistry. — Male-fern contains the crystallizable or 

 amorphous filicic acid whose reputation as the sole active 

 constituent is disputed. It is, at least in the crystalline 

 state, odorless, tasteless, insoluble in water except with an 

 alkali, but quite soluble in absolute alcohol and ether. 

 Other constituents are filicic tannic acid (10 per cent.), 

 fixed and volatile oil, resin, sugar, and starch. 



CALAMUS. 



The rhizome of Acorus Calamus, Linne (nat. ord. 

 Aroidece). 



Habitat. — Europe and North America, in wet meadows 

 and on the banks of streams and ponds. 



Description. — In sections of various lengths, unpeeled, 

 about 2 cm. broad, subcylindrical, longitudinally wrin- 

 kled ; on the upper surface marked with leaf-scars forming 

 triangles, but on the lower surface with the circular scars 

 of the rootlets in wavy lines; externally reddish-brown, 

 somewhat annulate from remnants of leaf-sheaths; 

 internally whitish, of a spongy texture, breaking with a 

 short, corky fracture, showing numerous oil-cells and 



