484 



GRAMINE^. CEREALS 



embryo does not make its exit where the coleorhiza and roots 

 emerge but grows on beneath the glume, and ultimately appears 

 at the opposite end of the grain sometime after the roots have 

 come forth (Fig. 151). 



The number of roots vis- 

 ible on the embryo within 

 the barley grain is generally 

 five or six. 



(c) In the oat the caryopsis 

 is free from the glumes, but 

 the latter more or less tightly 

 surround it and on germina- 

 tion the plumule of the em- 

 bryo behaves as in barley, and 

 emerges from the grain at the 

 end opposite to that at which 

 the roots appear ; the number 

 of roots of the embryo is 

 three. 



Roots.- — In the cereals, as 

 in all grasses, the roots of 

 the embryo within the seed 

 „,'.,''. , ,. grow out when germination 



Fig. 151. — Barley gram showing embryo and Its " o 



development during germination. commcnces : these may be 



1. Longitudinal section of grain showing ■' 



embryo at rest. . . , , , iexmed 'semifta/' roofs. They 



2. The same alter germination has begun ; the 



roots have made tlieir exit from the grain, but the are of importance m the early 

 plumule c is still within it enclosed by the ^ 



flowering glume. life of the young plant, but 



3. Later stage of the germinated gram showing , ,. -- n 1 ■ 



the plumule c outside the grain. Subsequently die off and their 



e Endosperm; a coleorhiza; i root; c plumule; . 



(^scuteiium. work IS Undertaken by the 



so-called 'coronal' roots which arise from the lower nodes of the 

 stems as explained below (see Figs. 152 to 154). 



'Tillering.' — A, Fig. 152 gives the appearance of a young 

 barley plant after a single green leaf has appeared above ground. 

 At this stage it possesses a small bunch of roots which have come 



