GERMINATION OF THE GRAIN 25 



angular portion opposite. An hour or two later the first pair of lateral 

 rootlets become visible, each with its thin covering root-sheath ; these 

 spring from the sides of the short hypocotyl almost in line with the base 

 of the epiblast (Fig. 18). 



Under favourable conditions the three rootlets and plumule grow 



FIG. 17. Base of germinating grains, showing rupture of the pericarp by the coleorhiza 

 and plumule of the growing embryo. 



rapidly, the former elongating much more quickly than the latter. The 

 primary root is for a time somewhat longer than the secondary ones, but 

 later there is little difference between them either in length or thickness. 

 Usually in three or four days, when the first rootlets have attained a length 

 of about 2 cm., two more appear, one on each side of the hypocotyl imme- 



FIG. 18. Young plants. />, Plumule ; , , coleorhiza ; i, primary root ; 2. root of first pair 

 of lateral roots; 3, root of second pair; 4, root above the epiblast, inserted at riht 

 angles to the others. 



diately above the first pair, a sixth rootlet sometimes developing later, 

 at right angles to the rest, from a point on the axis behind the epiblast 

 (Fig.^iS). 



The germination of the naked caryopses of T. monococcum, T. dicnccum, 

 and 7\ 5pi//<i is similar to that of other wheats : sprouting is, however, 



