2.48 THE STRUCTURE OF ECONOMIC PLANTS 



the manner in which the secondary or lateral roots arise. Typi- 

 cally, the beet has a single tap root, but it may branch to form 

 several fleshy members. 



The Leaves. — The large succulent leaves of the basal rosette 

 are arranged in a close spiral in a ^{3 phyllotaxy, and are extremely 

 variable as to size, shape, and color. In general, the petiole 

 is somewhat triangular in transection and more or less flattened 

 at the base. The lamina is prominently veined and the lateral 

 branches which arise from the main veins form a netted system in 

 which some of the small veinlets anastomose, while others end 

 blindly in the mesophyll. The blade is elongated, somewhat 

 oblong or triangular with a cordate base, its margins may be 

 straight or undulate, and the surface is smooth or crinkly. There 

 is an equally wide variation with respect to color, which ranges 

 from dark red to a light green. The rosette of leaves produced 

 the second year resembles that of the first but they are progressively 

 smaller. 



The Inflorescences and Flowers. — The stem elongates 

 rapidly to form the floral axis, and the development of numerous 

 branches which arise from the axillary buds of the basal leaves 

 results in the bushy habit of the mature plant. The terminal 

 portions of the main axes and lateral branches produce inflores- 

 cences which are paniculate or spicate in character. (Fig. 118.) 

 The flowers are sessile and occur singly or more commonly in 

 clusters of two or three. They arise from a very short floral branch 

 subtended by a large median bract and two lateral ones which 

 bear flowers in their axils. The flowers are perfect and consist 

 of five narrow sepals, five stamens, and a tricarpellate pistil. The 

 ovary of the mature pistil forms a fruit which is embedded in the 

 base of the perianth of the flower, and these are enclosed by the 

 common receptacle of the flower cluster so that a multiple fruit or 

 "seed ball" is formed by the cohesion of two or three such enclosed 

 fruits. The fruit is hard, containing a single seed and, where 

 flowers occur singly, forms what is known in commercial practice 

 as a "single germ beet seed." When the "seed ball" is formed by 

 the aggregation of two or three flowers, the so-called "multiple 

 beet seed" is produced. These terms, of course, refer to the fruits, 

 as the true seeds are small, dark, kidney-shaped structures. 



Seed Production. — The annual method of producing sugar 

 beet seed was developed by Overpeck (13) in New Mexico about ten 



