362 



Introduction to Botany. 



are pubescent on the under side. The flowers are white, 

 from three-fourths to one inch broad, and the black pulpy 

 fruit is from one-half to one inch long, and has a pleasant 

 flavor. The individual plants are essentially alike, their 

 common ancestry is very evident, and we class them ac- 

 cordingly, under one species. 

 The running swamp black- 

 berry, Rubus hispidus (Fig. 

 195), has slender creeping 

 stems, beset with weak bris- 

 tles. From the creeping stems 

 more or less erect branches, 

 nearly or quite destitute of 

 prickles, arise to a height of 

 four to twelve inches, and bear 

 leaves of three, rarely of five, 

 obovate leaflets whose mar- 

 gins are irregularly and 

 sharply serrate above the 

 middle. The white flowers 

 are one-half to two-thirds of 

 an inch across, and the black, 

 sour fruit is less than one-half inch long. 



No one would consider that these two blackberries had 

 arisen by suckers or seeds from the same stock, and they 

 are accordingly classified under different species ; but still 

 they have so many structural characteristics in common 

 that they apparently sprang from a common ancestor some- 

 where back in their lineage. We note, for instance, that 

 each has flowers consisting of a deeply five-parted calyx 

 with a shallow, broad tube ; five petals, numerous distinct 

 stamens inserted on the calyx, several two-ovuled carpels 

 inserted on a convex receptacle, which in ripening become 



FIG. 195. 



Rubus hispidus. After BRITTON and 

 BROWN. 



