288 SYSTEMATIC BOTANY 



Examine carefully the flower of a Stock, Wallflower 

 or Mustard (or any of "those) mentioned above. The 

 flowers are always in racemes, with no bracts or 

 bracteoles. The sepals always four, the petals four, 

 with long claw and horizontally spreading limb. Of 

 the six stamens notice that the short ones stand oppo- 

 site two sepals, while the four long ones stand in 

 pairs opposite the other sepals. Obviously, therefore, 

 each pair of long stamens is derived by splitting from 

 one, which would stand naturally opposite that sepal 

 (compare chapter xx, p. 220 where similar evidence is 

 adduced in support of the idea that a bunch of stamens 

 has been derived from one by a process of splitting). 



Note too that the two sepals which correspond to 

 the short stamens bulge out slightly at the base. 

 This is to make room for the secretion of honey at 

 the bottom. The flower of the Candytuft is irregular, 

 two petals being larger than the other two, but 

 almost all other CRUCIFER^E have perfectly regular 

 four-merous flowers. 



MALVACEAE 



Examples: 



SlDA HUMILIS. A herb with slender procumbent 

 branches found everywhere in the hotter parts of 

 India. The whole plant is more or less hairy, with 

 both simple and short branched hairs, especially on 

 the younger parts. Leaves alternate, stipulate, petioled, 

 broadly ovate, acute, serrate. 



Flowers on axillary branches, with bracteoles where 

 they branch again, or perhaps only a joint at about 



