150 



or the assiunptiom of functions other than usual. Tlie morphological 

 character of those parts may, liowever, usually he recognised from 

 their position in the spikelet and from comparison with allied, less 

 modiiied species. Reduction or suppression is frequent in the glumes, 

 less so in the pales, and it is extremely rare in the valves, except the 

 reduced tiorets. The lower valves, are, in certain tribes, frequently 

 without a flower ; but they often enclose a rudiment of a floral branch 

 let, in the shape of a perfect or reduced pale, thereby indicating tlieir 

 homology with typical valves. In this case, they often lose some of 

 the characteristics of the fertile valves, and approach either to the 

 glumt;s in their structure, or assume some special structure differing 

 from that of the glumes as well as from that of the fertile valves. The 

 nervation of the valves is very constant in nearly all the genera, and 

 often throughout the greater part of a tribe ; but in order to see it 

 clearly, it is always advisal)le to flatten the valve and to examine it by 

 transmitted light in a drop of water. When the sexual conditions of 

 the florets are of importance, it should be kept in mind, that many 

 grasses are very distinctly protandrous, i.e , that they shed their 

 anthers some time before the stigmas expand. Such flowers have 

 frequently been taken to be female, whilst they were actually her- 

 maphrodite. To avoid this error, young spikelets should, if possible, 

 be examined beside the fully developed ones, or the iilaments which 

 usually remain around the ovary should be sought for. 



SERIES I. 



Mature spikelets falling entire from their pedicels or with them 

 (rarely subpersistent on a flat, indistinctly and tardily disarticulating 

 rhachis ; Stenotaphrum) all alike or differing in sex and structure ; 

 perfect spikelets with 2 heteromorphous florets, the upper hermaph- 

 rodite, the lower male or barren ; rhachilla not continued beyond the 

 upper floret. 



Spikelets falling entire, singly or in clusters, occur in the following 

 genera belonging to the second series ; Holcus ; Cha^tobromus ; Poly- 

 pogon ; Perotis ; Tragus; Desmostachya ; Spartina ; Lamarckia; 

 Fingerhuthia ; UrochUcna ; Tetrachne ; Entoplocamia. 



'J Vibe 1. Andropogoaeai Spikelets usually in pairs, one sessile, 

 the other pedicelled (sec Trachypogon), rarely 3-nate or solitary on 

 the axes of variously arranged, often spikelike racemes. Glumes more 

 or less rigid and firmer than the valves, and the lower always longer 

 than the florets. Valves mem})ranous, often hyaline, that of the upper 

 floret generally awned or reduced tcj an awn. 



Tmj)erata ; Saccharum ; Erianthus; Pollinia ; Ischaemum ; 

 Uottboellia ; Urelytrum ; Trachypogon ; Elionurus ; Andropogon ; 

 Anthistiria. 



Tribe 2. Paniceae. Spikelets in usually continuous spikes, racemes 

 or panicles (Uumes herbaceous or membranous, the I'jwer smaller 

 very small or suppressed. Lower valve generally resembling 



