190 BOTANY. 



starch of flour. They break up the starch, and in the 



process liberate considerable 

 quantities of carbon dioxide, 

 which appears as bubbles upon 

 the surface of the yeast. An- 

 other result of the breaking up 

 of the starch is the formation of 



Fto. 112. — Yeast-plants in 



various stages of growth; (land alcohol ; heuce the fifrowth of 



?). c, a spore-sac containing four ' ° 



ITS'^rd^i^ll.^^^m, yeast-plants in a starchy sub- 

 c and a magnified 750, times. ^^^^^^ jg ^j^^yg accompanied by 



what is known as alcoholic fermentation. The housewife 

 and baker use yeast-plants for the carbon-dioxide gas which 

 they evolve, to give lightness to the bread, while the 

 brewer and distiller use the same plants for the alcohol 

 produced by their activity. 



Practical Studies. — (a) Searcli for cup-shaped fungi, in the spring, 

 about old hot-beds and upon well-rotted barnyard-refuse. The com- 

 mon Cup-fungus of an amber color (Peziza vulgaris) often to be met 

 with in such localities is one of the best for the study of spores and 

 spore-sacs. Malie very thin sections at right angles to the inner sur- 

 face. This species may be readily preserved in alcohol for future 

 study. 



(J) Collect the bright-red saucer-shaped plants growing in the 

 woods upon decaying sticks and having a diameter of 1 to 4 cm. 

 Make similar sections. 



(c) Collect a few Morels (Morchella esoulenta), and make sections at 

 right angles to the surface of the pits which cover its upper portion 

 for spores and spore-sacs. The Morel, which grows in the woods, is 

 an amber- or straw-colored fungus 10 to 15 cm. high and having an 

 egg-shaped pitted top, 3 to 6 cm. in diameter, borne upon a thick 

 stalk, both stalk and top being usually hollow. The whole growth 

 above ground (which is edible) is to be regarded as a spore-fruit. 



(d) Collect fruiting specimens of the common fruticose lichen 

 shown in Fig. 108, B, which grows upon branches of trees in forests. 

 Make thin cross-sections of the stem, mount in alcohol, afterwards 

 adding dilute potassic hydrate. Study the iilaments, and their rela- 

 tion to the gonidia. Isolate some of the gonidia by tapping on the 

 cover-glass, and note their resemblance to Green Slime, 



