INTRODUCTION TO BOTANY. li 



pericarp bursts near the dissepiments, which remain free and 

 ewtire on the separation of the valves^ the dehiscence is called 

 septifragal, as in bignonia, and calluna vulgaris. 



The organization of the pericarp, and seed is one of the 

 most difficult parts of botany. To give a clear idea of the 

 parts, an analysis of the fruit of the common peach (amy'gda- 

 lus persica) is here given. 



The fruit is composed essentially of two parts, the pericarp 

 and the seed. The seed is always contained within the peri- 

 carp. Let a peach be cut in two : its centre is found occu- 

 pied by a cell or cavity, containing a single seed, and rarely 

 two. All outside the seed belongs to the pericarp. First, 

 on the outside, is a thin coloured pellicle, covered with a soft 

 down, easily removed ; this is the pericarp. The internal 

 cavity of the pericarp, lined with another soft membrane, 

 adhering intimately to the hard part, which forms the nut, is 

 called the cndocarp. The whole of the thick, fleshy substance, 

 contained between the latter membrane and the epicarp forms 

 the sarcocarp. The nut or bony part in the centre of the 

 peach is formed of the endocarp, to which is added an ossi- 

 fied portion of the sarcocarp. We find similar parts as above 

 described, in the apricot, plum, cherry, &c. 



We will next give an analysis of the comrnon pea fruity 

 (pisum sativum.) 



The two longitudinal sutures, indicate that the fruit, when 

 ripe, opens by two segments or valves : hence it is called, a 

 two-valved pericarp. This pod, is found to have a single 

 cavity, with eight or ten seeds, in other words, it is one celled, 

 and many seeded. Every thing outside the seed is a part of 

 the pericarp. On the outer surface is a thin membrane 

 closely adhering to the subjacent part; this is the epicarp. 

 The inner cavity is lined with another membrane, which 

 adheres less intimately; this is the endocarp. The fleshy, 

 green, vascular part, between the two membranes, though not 

 very thick, is the sarcocarp. The small, longitudinal promi- 

 nence, which runs along the sutures, and to which the seeds 

 are attached, is the tropJwsperm, or placenta. 



Each of its prolongations belonging to a particular seed, is 

 a podospermy or umbilical cord. 



e2 



