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PRINCIPLES OF PLANT CULTURE 



a — The calyx ; when divided, the parts are called 



sepals. 

 b — The corolla ; when divided, the parts are called 



petals, 

 c — The stamens ; the parts are the filament, anther 



and pollen. 

 d — The pistil or pistils ; the parts are the stigma, 



ovary and style. 

 The ovary contains the ovule or ovules. 



145. Variation in form. — The parts of the flower 

 vary in form in different species. In the pea flower (Fig. 



46) the five petals, 

 shown separately 

 in Fig. 47, are not 

 only quite unlike 

 the petals of the 

 cherry flower, but 

 as appears, they 

 are unlike each 

 other. The sta- 

 mens (Fig. 48 st) 

 and the pistil (Fig. 

 49) of the pea are 

 also quite different 

 in form from those 

 of the cherry.' The 

 variety of form in the parts of the flowers of different 

 species is almost infinite. 



146. Abortive parts. — Certain parts of the flower 

 are often wanting. The flowers of the maple have no 

 corolla; those of the willow have neither calyx nor 

 corolla; certain flowers of the pumpkin, Indian corn 



Fig. 50. — Cross-section of flower-head of sun- 

 flower, Helianthus annuus. Reduced. The 

 florets appear closely crowded in the center 

 of the head. 



