PRACTICAL COURSE IN BOTANY 





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1 2 



Figs. 1-3. — The world's three most important food grains (magnified) : 1, sec- 

 tion of a rice grain ; a, cuticle ; b, aleurone, or protein layer ; c, starch cells ; d, germ ; 

 2, section of a wheat grain ; k, germ ; s, starch ; a, gluten ; t, t, t, layers of the seed 

 coat ; 3, section of a grain of corn ; c, husk ; e, aleurone layer containing proteins ; 

 eg, yellowish, horny endosperm, containing proteins and starch ; ew, lighter starchy 

 endosperm : the darker part below is rich in oil and proteins, and contains the eni' 

 hryo, consisting of the absorbing organ, or cotyledon, sc; the rudimentary bud, s ; and 

 the root, w. (1, from Circular 77, La. Exp. Station ; 2, from France ; 3, from Sachs.) 



2. Why food is stored in seeds. — The one purpose 

 for which plants produce their seed is to give rise to a new 

 generation and so carry on the life of the species. The 

 seed is the nursery, so to speak, in which the germ destined 



to produce a new plant 

 is sheltered until it is 

 ready to begin an inde- 

 pendent existence. But 

 the young plant, like 

 the young animal, is 

 incapable of providing 

 for itself at first, and 

 would die unless it re- 

 ceived nourishment from 

 the mother plant until 



Figs. 4-7. — Sections of corn grains showing -j. v r i j. j 



different qualities of food contents : 4, 5, small ^^ '^^^ lOrmeQ rOOtS anQ 



germ and large proportion of horny part, show- leaVCS SO that it CaH 



ing high protein; 6, 7, large germ and smaller pro- c -l r J r 



portion of horny part, showing high oil content, manuiacture lOOd lOr 



