288 BOTANY AND PHARMACOGNOSY. 



a black or bluish-black epicarp, a brownish sarcocarp, and a hard, 

 oval, smooth and flattened endocarp. 



The endocarps of the members of the genus Prunus vary 

 greatly. The endocarp in the apricot (P- armeniaca) is quite 

 smooth as is also that of the cherry (P. Cerasus) ; in the peach 

 {Prunus persica) it is reticulate. 



The apple (Pyrus mains), the pear (Pyrus communis), and the 

 quince (Cydonia vulgaris) are inferior fruits known as pomes, 

 the fleshy part developing from the torus and persistent calyx, 

 the core being composed of the united carpels. The edible fruits 

 of the Rosaceas contain a number of fruit-acids, such as malic, 

 citric, tartaric, and fruit-sugars, as dextrose and levulose. The 

 acids vary from 0.20 per cent, in pears to 1.50 per cent, in 

 plums; and the sugars from 4.48 per cent, in peaches to 8.26 

 per cent, in pears. The carbohydrates mannit and sorbit are found 

 in the fruit of Prunus Lauro-cerasus of Europe. In the unripe 

 fruits there is more or less tannin and also a principle known as 

 PECTOSE. This latter during the ripening of the fruit is converted 

 into PECTIN, a viscid principle which is further changed into pectic 

 and pectosic acids, the solutions of which gelatinize on cooling, 

 so that these fruits are adapted to jelly making. 



Rubus nigrohaccus, or high bush-blackberry, is a branching 

 shrub I to 2 M. high with reddish, prickly, erect or recurved 

 stems. The leaves are 3- to 5-foliate, the leaflets being ovate, 

 coarsely and tmequally serrate, and midrib and petiolules with 

 stout, recurved prickles. The flowers are white, in terminal 

 racemes and with hairy and prickly stalks. The fruit is broadly 

 ovoid and consists of an aggregate of drupelets which ripen in 

 August and September (Fig. 232). 



Rubus villosus Ait. (Rubus canadensis L.) or low-black- 

 berry (Northern dewberry), is a trailing, shrubby, prickly plant 

 the leaves of which are 3- to 7-foliate, the leaflets being oval or 

 ovate-lanceolate, serrate and nearl}' smooth. The flowers are in 

 racemes and the fruit resembles that of R. nigrobaccns, but is 

 smaller. 



Rubus cnneifoUus or sand-blackberry of the Eastern and 

 Southern States is a small shrub less than i M. high, much 

 branched, and with straight or recurved, stout prickles. The 



