314 



BOTANY. 



viz., one in wliich the stamens are long and the styles short, and 

 the other with short stamens and long styles, the flowers are said to 

 be dimorphous, or, more accurately, heterogonous dimorphous, and the 

 forms are distinguished as short-styled and long-styled. 



Examples of dimorphous flowers are common in many genera of 

 plants; e.g., in Bluets (Houstonia), Partridge berry (Mitchella), 

 Primrose (Primula), Puccoon (Lithospermum), Buckwheat (Fago- 

 pyrum), etc., etc. (Figs. 213 and 214). 



When, as in some species of Oxalis, there are three forms, viz., 

 long-, mid-, and short-styled, the term trimorphous (or, better, heter- 

 ogonous trimorphous) is used (Fig. 215). 



§ 6. The Frtjit. 



Structure — The fruit may include (1) only the ripened ovary 

 (pericarp) with its contained seeds — e.g., the bean ; or (a) these with 

 an adnate calyx or receptacle — e.g., the apple. 



Fig. 215. — Long-, mid-, and short-styled flowers of Oxalis speciosa, 

 after the removal of the floral envelopes. (From Darwin.) 



During the ripening changes in structure may take place, as (1) 

 the growth of wings or prickles ; (2) the thickening of the walls 

 and the formation of a soft and juicy pulp ; (3) the hardening of 

 some portions of the ovary- wall by the development of stony tissue ; 

 (4) the thickening and growth of the adnate calyx or receptacle, 

 etc., etc. 



Where the ripening walls remain thin and become dry, the fruits 

 are said to be dry, e.g., in the bean ; where they become thickened 

 and more or less pulpy, they are fieshy, e.g., the peach. These 

 terms are used also when the fruit includes an adnate calyx or re- 

 ceptacle. 



In many fleshy fruits (developed from carpels) the inner part of 

 the pericarp- wall is hardened ; the two layers are then distinguished 

 as exocarp and endocarp ; when there are three layers, the middle one 

 is the mesocarp. 



