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TEXTBOOK OF BOTANY 



"vegetables." Vegetable salads may even contain the seeds of beans and 

 peas. The term "vegetable" is not a technical term. Sometimes it is used 

 synonymously with the term "plant," as in the expressions "vegetable 

 kingdom" and "vegetarian." We shall soon see that in everyday language 

 the fruits of many plants are not ordinarily distinguished from seeds. 



Types of fruits. The variety of fruits appears to be as great as that of 

 the flower from which they develop. In the course of a year everyone 

 eats or otherwise encounters many types of fruits, and it may be of 

 interest to be able to recognize the principal structures of the more 

 familiar ones. Botanists and horticulturists often try to distinguish two 

 general types of fruits: the shnple fruits, which develop solely from an 

 ovulary or pistil, and complex fruits, which develop from ovularies and 

 a variety of adjacent structures. Fine distinctions are not always made. 

 A tomato, for example, is usually regarded as a simple fruit, although, as 

 in the fruit of pepper (Fig. 140), the placenta probably originates mainly 

 from the apex of the receptacle. 



Several types of simple fruits are easily recognized. If young bean 

 pods and young peach fruits are cut crosswise, the cut surfaces of 



Fig. 161. Cross section of three young simple fruits each composed of a single 

 carpel. The ovules develop from the infolded margins of the carpel, best seen 

 in C, which is a cross section of a very young pistil of a plum flower. A, cross 

 section of a young bean pod in which one ovule is evident; B, cross section of a 

 young peach with two ovules; D, cross section of a plum in which one of the 

 two ovules has failed to become a seed. The cells in the innermost tissue of the 

 carpels of peach and plum ultimately become thick-walled and form the hard 

 "pit" or "stone" of the fruit. 



these two types of fruits are seen to have certain features in common 

 (Fig. 161). Each consists of a single carpel with united margins. The 

 ovule or young seed visible in each section is attached by a short stalk 

 to one of the enfolded margins of the carpel. The bean pod may con- 



