CLASSIFICATION OF ANGIOSPERMS. 563 



of the Rosacese 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 Primus Laurocerasus 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 (see pp. 243, 255). 



Rubus nigrobaccus, 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 unequally serrate, and midrib and petiolules with stout, re- 

 curved 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. 



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

 (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 nearly smooth. The flowers are in racemes 

 and the fruit resembles that of R. nigrobaccus, but is smaller. 



Rubus ciineifolius 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 

 leaflets are ovate or cuneate, and densely pubescent, as are also 

 the young shoots. The inflorescence consists of two to five flowers, 

 the petals of which are white or pinkish. The fruit is oblong, more 

 or less cylindrical, and sometimes 20 mm. long. 



Rubus Idocus or the cultivated European red-raspberry is a 

 shrub with a glaucous, bristly stem and with 3- to 7-foliate leaves. 

 The flowers are white and the red fruit consists of a cap-like col- 

 lection of hairy drupelets which is easily detached from the non- 

 fleshy receptacle. The fruit is used in the preparation of syrup 

 of raspberry which is used for flavoring. There are a number of 

 varieties of this species of raspberry in cultivation, the fruits of 



