STKUCTUBB OF THE FLOWEK AND ITS ORGANS. 143 



as the essential organs. Fig. 116. The simplest possible pistil 

 is a dwarfed and greatly modified leaf (§ 188), adapted into 

 a seed-bearing organ. Such a pistil may be one-seeded, as in 

 Fig. 169, or several-seeded, as in the right-hand part of Fig. 

 171 ; it is called a carpel. The calyx and corolla are known 



ABC 

 Fig. 116. — The Essential Organs. 

 A^ stamens and pistil of a tulip (the perianth removed) ; s, stamens ; ^, pistil ; 



B, a separate stamen, with its anther a discharging pollen ; /, the filament ; 



C, pollen-grains. 



as the floral envelopes. Flowers which have the essential 

 organs are called perfect flowers. They may therefore be 

 perfect without being complete. In cases where the perianth 

 contains only one row of parts, it is assumed 

 that the petals are lacking. Such imperfect 

 flowers are said to be apetalous, Fig. 117. 

 176. Regular and Symmetrical Flowers. 

 — A flower is regular if all the parts of 

 the same set or circle are alike in size and 

 shape, as in the stonecrop, Fig. 118. Such 

 flowers as that of the violet, the monkshood, 

 the nasturtium, or the laburnum, Fig. 119, 

 are irregular. Symriietrical flowers are 

 those whose calyx, corolla, circle of stamens and set of carpels 

 consists each of the same number of parts, or in which the 



Fig. 117.— Apetalous 

 Flower of (European) 

 Wild Ginger. 



