CALYX. 



57 



awn, a bristle shaped appendage. This is sometimes spiral 

 or twisted, and possesses the property of a hygrometer. This 

 is the case with the awns of the Wild, or Hygrometic oat, 

 (Avena sterilis,} which are employed to construct an instru- 

 ment designed to indicate the decrees of moisture and 

 dryness. 



For this purpose the middle part of the Fi ^- 106 - 



awn, Fig. 106, which is twisted or formed 

 like a screw, is used, one end being cement- 

 ed to the centre of a circular plate, which is 

 marked off into degrees ; to the other end is 

 attached a bristle as an index, or hand. The 

 whole being covered with a glass, forms the 

 hygrometer, or moisture measurer. When 

 the weather is damp or rainy, the awn un- 

 twists and moves the hand in one direction, 

 but as the atmosphere becomes dry, it ceases 

 at first to move, and then turns in the con- 

 trary direction. The moisture of the hand 

 will set these awns in motion, making them appear like living 

 animals 



Fig. 107. 



Volva, Fig. 107, Wrapper. This is the 

 membranous covering of some of the Fungus 

 or Mushroom tribe, while young. The mem- 

 brane, as the vegetable increases in size, 

 finally bursts, and afterwards contracts and 

 dries, forming a kind of ring around the stipe, 

 or stem of the Mushroom, as represented in 

 the figure. 



Fig. 108 



Calyptra, Fig. 1 08, a Cap, or Hood. This kind 

 of calyx is found only among the mosses. It is 

 the cap or veil which covers the fructification of 

 many of that tribe. The shape is conical, resem- 

 bling that of an extinguisher, or thimble. These 

 plants are very common in the woods, and among 

 rocks, growing an inch or two high. 



What philosophical instrument is made by means of the awn of the hy 

 grometic oat ? What part of a mushroom is the volva, or wrapper 

 What part of a moss is the calyptra, or hood ? 



