HOW PLANTS GROW FROM THE SEED. 



15 



embryo imbibes and feeds on as it sprouts. That the meal or starch of the grain 

 is actually changed into sugar at this time is clearly shown by malting, which is 

 merely causing heaps of grain to sprout a little, and then destroying the life of 

 the embryo by dry heat ; when the grain (now malt) is found to be sweet, and 

 to contain much sugar. 



36. The nouvlr^hment which the mother-plant provides in the seed is not always 

 stored up outside of the embryo. In many cases it is deposited in the embryo 

 itself, most commonly in the seed-leaves. Then the seed consists of nothing but 

 the embryo within its coats. Maple-seeds are of this sort. Fig. 24 represents a 

 seed of Eed Maple in the lower part of the winged seed- 

 vessel, which is cut away so as to show it in its place. Fig. 

 25 is the seed a little magnified, and with the coats cut away, 

 bringing to view its embryo coiled up within and filling the 

 seed completely. Fig. 26 is the embryo taken out, and a 

 little unfolded ; below is the radicle or stemlet ; above are the 

 two seed-leaves partly crumpled together. 

 Fig. 27 is the embryo when it has straight- 

 ened itself out, thrown off the seed-coats, 

 and begun to grow. Here the seed-leaves 

 are rather thick when they first unfold ; this 

 is on account of the nourishing matter which 

 was contained in their fabric, and which is 

 used mainly for the earliest growth of the 

 radicle or stemlet, and for the root formed 

 at its lower end, as we see in the next fig- 

 ure (Fig. 28 : a, the radicle or stemlet of the embryo ; h, h, the two seed-leaves ; 

 c, the root). By this time the little stock of nourishment is exhausted. But the 

 plant, having ah-eady a root in the soil and a pair of leaves in the air, is able to 

 shift for itself, to take in air, water, &c., and by the aid of sunshine on its foliage 

 to make the nourishment for , its future growth. In a week or two it will have 

 made enough to enable the next step to be taken. Then a little bud appears at 

 the upper end of the stemlet, between the two seed-leaves, and soon it shows 

 the rudiments of a new pair of leaves (Fig. 28, d) ; a new joint of stem forms to 

 support them (Fig. 29) ; this lengthens just as the stemlet of the embryo did, and 

 so the plantlet gets a second pair of leaves, raised on a second joint of stem 

 2 



