VARIETIES OF STRUCTURE. DISK. 3U5 



freed from it. The stamens too, not unfrequently seem to arise 

 from the corolla, instead of from the axis of the flower; but this 

 effect is produced in a similar manner namely, by their adhe- 

 sion at their lower part, to the inner side* of the petals. The 

 stamens, again, sometimes adhere to each other, so as to form a 

 complete tube, surrounding the pistil. 



467. In the foregoing instances, the symmetry of the flower 

 is not destroyed ; that is, it may be divided into two similar 

 halves by a line crossing it in any direction. But there are many 

 irregularities resulting from the unequal development of the 

 different parts of the same whorl, and from the adhesion of these 

 parts to each other in various ways ; so that the whole form of 

 the flower sometimes appears completely changed, and there is 

 only one direction, in which it can be divided into two equal 

 halves. This is the case in the flower of the Pea or Bean, for 

 example ; in which, as in other plants of the Papilionaceous 

 group (so named from the resemblance of the flower to a Papilio 

 or Butterfly), there is one broad petal standing erect, two sepa- 

 rate ones termed the wings, which are prolonged from its base, 

 and two others united together, forming what is termed the 

 keel, which is enclosed between the last. 



4G8. The flower is usually placed at the end of the flower- 

 stem, or of its subdivision of it ; and the tendency in this stem to 

 lengthen, appears to be checked by the development of a flower- 

 bud. It commonly swells out at the insertion of the perianth, 

 forming what is called the disk or receptacle; and in this, as for- 

 merly stated, nourishment is frequently laid up, in the form of 

 starch, for the development of the young ovules (. 285.) "This 

 receptacle sometimes grows upwards between the carpels, and 

 even encloses them. In other cases, it extends so much, as to 

 separate the carpels from one another; this is the case in the 

 Strawberry, of which the fruit is the swollen receptacle, whilst 

 the little bodies scattered over its surface (commonly termed 

 seeds) are in reality the carpels. Sometimes, however, it happens, 

 that the flower-stem continues to grow between the points, from 

 which the solids proceed ; and they are then separated from each 

 other, just as are leaves in like circumstances (. 304). The spiral 



