224 



PLANT LIFE. 



sarily ruptured to permit the escape of the spores, being 

 often displaced in the development of the sporangium, so 

 that at maturity it is partially free. 



Fig. 223. — A mildew (Erysipke communis), showing the mycelium ramifying over a 

 bit of leaf, with erect spore-bearing branches and globular fructifications, containing 

 asci. Magnified about 175 diam.— After Tulasne. 



318. Compound sporangia. — Simple sporangia occur only 

 among the lower plants. In the higher plants, including 

 the mossworts, fernworts, and seed 

 plants, the sporangium is always 

 compound. 



319. Development. — ( Compound 



sporangia may be developed either 



from superficial or from internal 



.. fr ! ,m cells. As a consequence, the mature 



the interior of the fructification ■ 



rxa\&vn<ErysipkeHeraciei\ sporangia will be either free or more 



similar to those shown in fig. 223. ' n 



Each as, us contains four spores. or l ess enclosed within the tissues of 



Magnified 200 diam. — After De- 



Bar y. the organ by which they are borne. 



A superficial cell may enlarge so as to protrude from the 



surface, and divide into two parts, of which the upper cell 



develops into the sporangium proper, and the lower cell into 



its stalk. According to this method of development the 



sporangium is a surface appendage, and may be looked upon 



