INFLORESCENCE AND FLOWER I 3 



CHAPTER III. 



THE INFLORESCENCE AND FLOWER. 



The flowers of grasses are reduced to their essential organs, 

 the stamens and the pistil. The flowers are aggregated together 

 on distinct shoots constituting the inflorescence of grasses. 

 Sooner or later all the branches of a grass-plant terminate in 

 inflorescences which usually stand far above the foliage leaves. 

 As in other flowering plants, in grasses also different forms of 

 inflorescence are met with. But in grasses the unit of the inflores- 

 cence is the spikelet and not the flower. 



The forms of inflorescence usually met with are the spike, 

 raceme and panicle. When the spikelets are sessile or borne 

 directly along an elongated axis as in Enteropogou melicoides the 

 inflorescence is a spike. If the spikelets borne by the axis are all 

 stalked, however short the pedicels may be, it is a raceme. It 

 must, however, be remembered that true spikes are very rare. An 

 inflorescence may appear to be a spike, but on a close examination 

 it will be seen to consist of spikelets more or less pedicelled. 

 Such an inflorescence, strictly speaking, is a spiciform raceme. 

 The branches of the inflorescence in Paspalum scrobiculatum or 

 Panicum javanicum are racemes and the whole inflorescence is a 

 compound raceme. The inflorescence is a panicle when the 

 spikelets are borne on secondary, tertiary or further subdivided 

 branches. Panicles differ very much in appearance according to 

 the relative length and stoutness of the branches. In Bragrostis 

 tremula the panicle is very diffuse, in Eragrostis Willdenoviamt 

 less so. The panicle in Sporobolus coromandelianus is pyramidal 

 and the branches are all verticillate, the lower being longer than 

 the upper. The branches of a panicle are usually loose, spreading 

 or drooping in most grasses. But in some species of grasses such 

 as Pennisetum Alopecuros and Setaria glauca, the paniculate inflores- 

 cences become so contracted that the pedicels and the short 

 branches are hidden and the inflorescence appears to be a spike. 

 Such inflorescences as these are called spiciform panicles. The 

 inflorescences in several species of Andropogon consist of racemes 

 so much modified as to appear exactly like a spike. What looks 

 like a spike in these cases consists of a jointed axis and each joint 

 bears a pair of spikelets, one sessile and the other pedicelled. 



The name rachis is given to the axis of the spike, raceme and 

 panicle, whether the axis is the main one or of the branch. The 

 rachis of the inflorescence is usually cylindrical. In some grasses 

 it is zig-zag" as in Pennisetum cenchroides. It is very much 

 flattened in Paspalum scrobiculatum, but somewhat trigonous in 

 Digitaria sanguinalis. In very many grasses the rachis is conti- 

 nuous, but in a few cases it consists of internodes or joints which 

 disarticulate at maturity. Many species of Andropogon have such 

 jointed rachises. Sometimes the joints become greatly thickened 



