BETA VULGARIS 



2-53 



and the cotyledons expand laterally. (Fig. iii.) The young 

 seedling consists of three regions, root, hypocotyl, and cotyledons; 

 and the point of transition between root and hypocotyl can be 

 determined with a fair degree of accuracy by the abrupt tapering 

 of the axis and by the location of the lateral roots. Epicotyledon- 

 ary development is slow; but after the complete expansion of the 



# 



Fig. 12.1. Habit of beet fruit and stages in development of seedling. 



cotyledons, the first pair of foliage leaves begins to grow rapidly. 

 This occurs about eight to ten days after germination and is fol- 

 lowed by the differentiation and growth of the foliage leaves 

 which form the primary rosette. 



ANATOMY 



The Cotyledons. — The fleshy cotyledons are single-nerved 

 and elongated with short petioles or tapering bases. Their 

 structure is simple and the mesophyll consists of chlorenchyma 

 in which there is little differentiation into palisade and spongy 

 tissues. The small vascular bundles are collateral and run longi- 

 tudinally between the spongy parenchyma and the palisade. 

 The epidermal cells are irregularly polygonal in outline with 



