STRUCTURE AND GERMINATION OF SEEDS 29 



green and act as the first green leaves. This mode of 

 germination is called epigeal (Gr. epi = upon). 



Allow the seedlings to continue their growth, compare 

 the successive leaves as they appear, and note that the first- 

 formed foliage -leaves are often simpler than the later ones. 

 In this respect the Sweet -Pea is an interesting example 

 to study. 



Development of the Sweet-Pea. Sow a few seeds in soil 

 and allow them to grow for several weeks, supporting the 

 tender stems with thin sticks. Note carefully each leaf 

 as it appears until the fully-matured ones are formed. 

 Compare the first or ' juvenile ' foliage-leaves with the later 

 adult leaves and try to determine the structure and uses 

 of the parts. 



As the arched shoot comes above ground (Fig. 131, 5, 

 p. 189), very small leaves appear ; the first is seen to consist 

 of two pieces or lobes, with a narrow pointed lobe between 

 them (Fig. 131, 6, t) ; the second leaf is a little larger, and 

 the lobes are better developed and toothed (Fig. 131, 7) ; the 

 third leaf still shows the two lobes close to the stem ; and 

 above these is a short leaf-stalk, then a pair of oval lobes, be- 

 tween which is a slender green thread (Fig. 131, 8). The two 

 lower lobes, or stipules (st), are outgrowths of the leaf -base; 

 they cover and protect the rest of the leaf in the bud. The 

 leaf-stalk and blade are represented at first only by the 

 narrow terminal lobe ; in the later leaves the blade develops 

 two large opposite lobes, and the terminal thread becomes 

 longer. Finally, the terminal part of the blade divides 

 to form paired structures agreeing in position with the 

 lobes of the blade, of which they are special modifica- 

 tions. Note their behaviour on coming into contact with 

 a stick, and you will see at once the use of this curious 

 modification as a clinging organ. In the older plant (Fig. 

 131, 1) these organs are well developed, and by twining 

 round a support enable the stems to grow up above 



