DEVELOPMENT OF PLANTS 429 



istic of the family) which fall with the opening of the flower, 

 petals 8-12, stamens indefinite and a compound pistil of two 

 carpels, as is indicated by the two stigmas and two rows of ovules 

 (Fig. 308, C). The stigmas are receptive as soon as the flower 

 opens, but the anthers remain closed, and so the spores must be 

 carried from an older flower. The petals close during the late 

 afternoon and when opened on the following day the anthers 

 shed their spores and complete the flowering. 



In higher types of the poppies we find the flowers becoming 

 irregular and the various parts reduced in numbers. Thus, in 

 the soldier's cap (Fig. 308, D), there are two scale-like sepals, 

 four petals in two pairs, the two outer heart-shaped and spurred 

 at the base, while the two inner are narrow and winged on the 

 back, enclosing the sporophylls. The six stamens are somewhat 

 united and arranged into two groups opposite the spurred petals. 

 The carpel has the same structure as in the bloodroot. It is 

 evident that the nectar concealed in this closed type of flower 

 can only be secured by some long-tongued insect. Find out how 

 the bee procures the honey, the purpose of the wings on the 

 narrow petals and the position of the nectar glands. Is the 

 stigma mature before the anthers open? The structure of this 

 higher type of the poppies makes the transition to the mustard 

 family a simple one. 



(b) The Mustard Family, Cruciferae. — Here we find the 

 sepals and petals four in number, and the latter arranged cross- 

 wise (Fig. 309, A, B), thus explaining the family name, Crucif- 

 erae. The petals usually have rather long claws (Fig. 309, D) 

 that are so associated with the sepals as to form a narrow tubular 

 perianth that effectually conceals the nectar glands situated at 

 the base of the ovary. There are usually six stamens, but the 

 two outer ones are shorter than the others (Fig. 309, C). The 

 ovary is divided into two compartments by a membranous parti- 

 tion. The fruit is generally a capsule that usually opens by two 

 valves, as seen in Fig. 309, F. This large family of over 1,800 

 species is almost universally distributed over the earth and of 

 very common occurrence. These plants with their small white 

 or yellow flowers aggregated in conspicuous inflorescences are 



