DEVELOPMENT OF PLANTS 



375 



The root is pushed out through the micropyle and bends down 

 into the soil, the hard integument often being cracked open by 

 the SwelHng of the cells. The cotyledons remain within the seed 

 until they have absorbed all the food from the gametophyte, 

 when they are withdrawn and become erect (Fig. 259). 



Fig. 259. Renewal of growth of the embryo. At the left a seed has been 

 cut across to show the relation of parts during the early growth. The in- 

 tegument has been ruptured by the swelling of the seed and the protrusion 

 of the root which is curving down into the soil. The cotyledons, c, remain 

 in the seed absorbing the food from the gametophyte or endosperm, g. At 

 the right a later growth with the cotyledons partially withdrawn from the 

 seed after the absorption of its food. 



(e) The Principal Genera of Finales. — The more important 

 genera of Pinales may be distinguished as follows: Pinus or 

 pine, leaves long and needle-like, borne in fascicles on short stems 

 that are quite concealed by papery sheathing scales (Fig. 251, i). 

 Larix or larch, short needle-like leaves clustered in tufts on short 

 lateral branches. This is the only northern member of the order 

 with deciduous leaves. Picea or spruce, leaves angled or four- 

 sided, radiating from all sides of stem, petioles remaining on 

 branchlet after leaves fall, thus causing the rough appearance of 

 the branchlets (Fig. 260, 9). Tsiiga or hemlock, leaves fiat in 

 two rows, the petiole remaining on tlie stem after fall of leaf; 



