382 PRIMITIVE FLOWERS 



hairs are associated with the sporophylls. These are supposed 

 to represent sterile sporophylls and this is borne out by the fact 

 that primitive flowers are characterized by just such an arrange- 

 ment of their sporophylls, and also by the fact that in an allied 

 genus spirally arranged sporophylls actually occur. These simple 

 types of flowers are often developed in large numbers upon an 

 elongated stem (Fig. 262, A, D~G) and are rather suggestive 

 of a strobilus although the individual flower really corresponds to 

 the strobilus, as will be seen especially in those types where 

 the sporophylls are numerous and arranged spirally upon the 

 receptacle of the flower (Fig. 264) . A group or cluster of flowers 

 is called an inflorescence in contradistinction to the solitary 

 flower developed at the end of a branch or stem. It is notice- 

 able in these primitive angiosperms that the micro- and mega- 

 sporophylls are usually borne in separate flowers or inflorescences 

 (compare Finales) which are developed on separate plants as 

 in the willow or on different parts of the same plant as in the 

 cat-tail. This arrangement is probably associated with the 

 fact that the advantages of crossing or the transfer of the micro- 

 spores of one flower to the megasporophylls of another is effected 

 by the wind. In higher types, which include^ the great majority 

 of angiosperms, the micro- and mega-sporophylls are developed 

 in the same flower which is therefore said to be perfect since it 

 contains both of the organs essential for seed production (Fig. 

 261A, i). A type like the willow is termed imperfect because 

 the flower lacks one kind of sporophyll. Crossing is effected 

 in the -perfect type of flower by the earlier ripening of the micro- 

 or mega-sporophylls and often also, by the arrangement of the 

 organs of the flower which is of such a nature that the microspores 

 cannot readily reach the mega-sporophylls of the same flower. 

 Insects are usually the agents for the transport of the micro- 

 spores in such cases. Flowers in which the microspores mature 

 and are shed from the anthers before the stigmas of the mega- 

 sporophylls are ready to receive them, are called protandrous, 

 meaning that the microspores which develop the male gametes, 

 are the first to mature. If the mega-sporophylls become recep- 

 tive before the anthers open, the flower is said to be pro togy nous. 



