DEVELOPMENT OF PLANTS 447 



By cultivation an abnormal development of one part or another 

 of the plant has been induced. This feature is well illustrated 

 in the cabbage, where the elongated stem of the wild plant has 

 become shortened by cultivation and covered with fleshy leaves, 

 forming a large bud or head. Brussels sprouts are a modifica- 

 tion of the cabbage in which the stem becomes more elongated 

 and covered with numerous small heads. The great variety of 

 kales are really headless cabbages in which the leaves remain free 

 from one another, assuming a variety of forms. The cauliflower 

 is a variety of the cabbage in which the inflorescence has been 

 transformed into a fleshy mass of tissue, and in the kohlrabi the 

 stem becomes swollen and herbaceous. The turnip is a related 

 species of the cg,bbage genus in which the underground portion 

 of the plant is modified. Radish, cress, horse-radish, caper, 

 spices and oils of mustard, etc., are other products of the order, as 

 well as many cultivated flowers, as the wallflower, stock, mig- 

 nonette, etc. 



144. Resales, the Rose Order. — This enormous order, com- 

 prising over 14,000 species, is better known than any other, not 

 only because of its great array of common. field plants, but espe- 

 cially because of the large variety of our cultivated fruits and 

 flowers that belong to it. The cultivated currant, blackberry, 

 strawberry, apple, pear, cherry, peach, plum, pea, bean, hydran- 

 gea, syringa, rose, spiraea, wistaria, laburnum, as well as many 

 native trees and shrubs, as the liquidambar, sycamore, witch- 

 hazel, locusts, etc., belong to the rose order. 



These plants may be looked upon as the most typical of the 

 Choripetalae, just as the Liliales were the most representative of 

 the monocotyledons. The parts of the flower are more com- 

 monly in fives and c^^cHc (Fig. 310, A) though the spiral ar- 

 rangement still persists in nearly every family of the order. The 

 most distinguishing feature of the group is seen in the basal 

 growth of the receptacle, thus lifting up the corolla and stamens 

 about the ovary (perigynous flowers) and this growth also fre- 

 quently results in the epigynous type of flower. The simple 

 forms of flowers that appear in many of the families are very 

 suggestive of the Ranales, the sporophylls being free and often 



