ASPIDIUM. 123 



The constituents of the powder, here describing both 

 powders under the same heading, are starch, parenchy- 

 matic tissue, thick- walled epidermal structures, vessels, 

 glands, and fragments of roots and chaffy scales. If 

 much stipe tissue is included in the powder, fibres may be 

 found. 



The starch grains are suggestive. They are usually 

 simple and exhibit a very great range both in size and 

 shape. In shape they vary from minute spheres to 

 flattened o voids, and in size from 2 or 3 microns to 4 to 6 

 or 8 to 12 microns. These larger grains often show small 

 apical irregularities, and are markedly flattened. The 

 hilum is not manifest. With polarized light it is seen 

 to be irregularly situated, sometimes centric, sometimes 

 eccentric; stratification lines are few in the ordinary 

 media used for observation, and with the polarizer, the 

 cross observed in so many of the starch grains is only in- 

 frequently seen. The parenchymatic cells are commonly 

 packed with starch grains. They vary in the character 

 of the cell wall, some thin, others thicker and pitted, with 

 irregular outlines, somewhat cuboidal in shape, and they 

 vary in diameter in the different parts of the same rhi- 

 zome ; measurements gave the range from 50 to 80 microns. 



Thick-walled epidermal structures are appreciable in 

 those powders which have been made from the rhizome 

 and stipes, in their natural condition; powders made 

 from peeled or prepared specimens lack this thick-walled 

 tissue. These cells are somewhat elongated and flat- 

 tened, with slightly wavy and thickened cell walls, not 

 infrequently sharp-pointed. Their color is dark-brown 

 to yellow, and when found they form a striking feature of 

 the powder. Cells from the outermost layers of this 

 cortical tissue have cell walls which are much thicker 

 than those further in. 



The vessels of aspidium are extremely large, and as a 

 rule, fragments only are found. These show the typical 



