84 THE EVOLUTION OF PLANTS 



species the number of stamens is about eighteen 

 or twenty; they are very large and complicated 

 organs, quite different from the stamens of any 

 Angiosperm or any other Gymnosperm. Each 

 stamen, if straightened out, would be about ten 

 centimetres (four inches) long; as a matter of 

 fact, however, they are always found folded in- 

 wards, as if the flower were still at the stage of a 

 bud (fig. 9). Each stamen is a pinnate leaf, with 

 about twenty pairs of leaflets, bearing the pollen- 

 sacs, which are ranged in two rows on each leaflet; 

 the longer leaflets bear as many as twenty pollen- 

 sacs each. 



The stamens are joined together by their 

 stalks, which thus form a tube surrounding 

 the female part of the flower, just as is the case 

 in the flower of a Mallow. Higher up, the 

 stamens become separate, and are bent inwards, 

 so that their tips reach down to their stalks. 



The pollen-sacs, borne in such large numbers 

 on the stamens, are themselves compound struc- 

 tures, for each sac is divided into numerous 

 compartments, in which the pollen was produced. 

 Such compound pollen-sacs are almost identical 

 in structure with the "synangia," or compound 

 spore-sacs of certain Ferns belonging to a small 

 tropical family, the Marattiacese (see fig. 17, p. 

 150). Indeed the stamens of Bennettitese were 

 altogether much more like the fertile fronds of a 



