CHAPTER XXVII. 



CRUOIFERJE. 



I. General characters of the Order. — Flowers (Fig. ii6, A), 

 regular, hypogynous. Calyx polysepalous, four sepals in two 



whorls, deciduous ; corolla 

 polypetalous, four petals in 

 one whorl : androecium of six 

 stamens in two whorls, /eira- 

 dynamous, that is, four sta- 

 mens with long filaments, and 

 two with short ones. (Fig. 

 II 6, B). Gynsecium (Fig. 

 ii6, C) syncarpous, two car- 

 pels : the ovules are arranged 

 on two parietal placentas ; the 

 ovary is sometimes unilocular, 

 but more frequently divided into two compartments by a ' false ' 

 partition, which is an outgrowth from the placentas. 



Fruit, usually a dehiscent silique or silicula (see Raphanus, p. 

 385), seeds without endosperm or with only traces of it. When 

 placed in water the cuticle of the testa of the seeds from the 

 dehiscent fruits generally swells up into a slimy sticky substance, 

 which fixes the seed to the ground, tends to store up water dur- 

 ing germination, and also aids in the distribution of the seeds. 

 Situated on the receptacle, generally atthe base of each of the 

 two short stamens, are greenish nectaries. 



Pollination is chiefly brought about by insects. The anthers 



are so placed in regard to the stigmas and nectaries, that insects 



365 



Fig. 116. — A^ Flower of turnip. ^, The same, 

 after stripping off the calyx and corolla, 

 showing the androecium and gynEecium. s Two 

 short stamens ; / four long stamens ;_ st stigma 

 of gynaecium; « nectary. C, Gynsecium. o Its 

 ovary ; b style; st stigma. 



