ORGANS OF REPRODUCTION. 191 



Fig. 389. Fig. 390. 



Fig. 389. Pistillate or carpellary amentum or 



catkin of a species of Willow [Salix). 



Fig. 390. Staminate amentum of Willow. 



the circumference of a dilated 

 axis are first formed, and those 

 nearest the centre or growing 

 point last, and therefore their 

 expansion will proceed from the 

 circumference to the centre: 

 hence all indefinite inflorescences 

 have a centripetal order of ex- 

 pansion. 



There are fire other kinds of 

 indefinite inflorescence which are 

 simply modifications of the spike. 

 These are the Amentum or Cat- 

 kin, the Spadix, the Locusta, the 

 Cone, and the Strobile. 



b. The Amentum or Catkin.— 

 This is a kind of spike which 

 only bears barren flowers — that 

 is, only staminate {fig. 390), or 

 pistillate (^fig. 389) ones. The 

 flowers of an amentum are also 

 usually separated from one 

 another by scaly bracts, and 

 the whole inflorescence (at least 

 as regards the staminate catkins) 

 commonly falls off in one piece, 

 soon after the process of flower- 

 ing, or fruiting. All plants with 



Fig. 391. Brancbed spadix of a 

 Palm (CliavicBrops), enveloped in 

 a spathe. 



