THE AMERICAN BOTANIST. 81 



Cxathiis vcniicosiis is the only species likely to be found 

 growing in unmanured ground. Sometimes it is attached to 

 buried sticks, but it rarely if ever grows on wood as the other 

 species do. Like C. striatiis it is of a wild nature, being found 

 usually on bare ground in fields, borders of woods and similar 

 places. It is readily known by the cups which are thicker, 

 firmer, more flaring, smooth inside and smoother outside than 

 the other species. The eggs or peridioles are black though 

 covered with a thin white membrane and are much larger than 

 any other species known. 



Cyathus stcrcorcus is a manure loving species and is usual- 

 ly found in manured ground such as lawns, gardens, fields, etc. 

 The cups are even inside and with shaggy hairs outside. When 

 old they become smoother and are sometimes mistaken for C. 

 veniicosus. When once learned,however, the plants can read- 

 ily be distinguished by the cups. The peridioles have no mem- 

 brane whatever, hence they are blacker than any other species. 

 They are about twice as large as those of C. veniicosus. The 

 first three species are usually abundant both in Europe and the 

 United States but C. stercorcus while common in the United 

 States is very rare in Europe. 



Aerenchyma. — One of the least known of plant tissues 

 is that which goes by the name of aerenchyma. As its name 

 indicates it is an aerating system being composed of large 

 thin-walled cells with large intercellular spaces. It is com- 

 parable to cork but unlike cork the cells contain no deposit 

 of suberin. Aerenchyma is usually if not always confined to 

 water plants. Sometimes it is found only at the lenticels, but 

 at others it forms a thick covering on submerged stems entire- 

 ly replacing the bark. Probably no plant in our flora better 

 illustrates aerenchyma than the water willow or swamp loose- 

 strife {Dccodon vcrticillatus). In this plant it is often an 

 inch in thickness. 



