ONION SMUT FUNGUS. 



119 



Section through a resting 



seed. 

 Longisection of a seedling 



four days after planting. 

 Successive stages in the de- 

 velopment from the third 

 day to the twenty-fifth 

 day. 

 Diagrammatic longisection 

 through the growing zone 

 at the end of two weeks. 

 Symbols for parts are the 

 same in all: 



sc, seed coat. 



en, endosperm. 



em, embryo. 



lb, leaf bud or primordium of 

 first leaf. 



re, root cap. 



r, radicle or first root. 



C7i, cotyledon. 



rj, root joint. 



kn, knee. 



al, ascending leg. 



dl, descending leg. 



CO, exterior opening of coty- 

 ledonary cavity. 



r2 and rS, first and second 

 secondary roots. 



cc, cotyledonary cavity. 



gp, growing zone, region of 

 origin of all leaves and 

 roots. 



lbs, primordium of second 

 leaf. 



Fig. 3. — Development of an onion seedling. 



