88 TYPES OF INFLORESCENCE [ CH. 
The Poa inflorescence is, however, different. It con- 
sists of a loose branched system of spikelets. Botanists 
term such a loosely branching system, where each branch 
ends in a flower, a panicle: here then we have a panicle 
of spikelets, or, shortly, a Panicle. Azra, Agrostis, Ca- 
lamagrostis, Avena, Catabrosa (Fig. 4) and many others 
afford further examples. 
In Dactylis we have a condition of affairs between the 
two extremes given: the inflorescence is not so close a 
spike as Nardus, and not so open a panicle as Poa—it is 
rather a spike-like panicle, partaking of the nature of 
both. A special type of this (Foxtail) occurring in certain 
grasses—e.g. Phleum, Alopecurus, Phalaris and Lagurus, 
—is so characteristic as to be worth noting (Fig. 3). 
There is also another aspect of these inflorescences 
which is not without interest as showing how diagnostic 
characters may be obtained from purely external features, 
easily observed in the field. We have seen that in 
Nardus the spikelets are arranged on one side only of 
the rachis, or main axis, so that about three quarters 
of the circumference of the latter is bare; whereas 
in Lolium—with which Agropyrum and Brachypodium 
agree in this respect—the spikelets are on opposite 
sides, leaving the intervening two quarters, 1e. half its 
surface, of the circumference of the axis naked. 
In Cynosurus and the simpler forms of Dactylis, we 
find the spikelets crowded round about three quarters 
of the surface of the rachis, leaving the fourth quarter 
naked; and, finally, in Phlewm, Alopecurus, Hordeum, 
and Anthoxanthum the spikelets cover the entire surface. 
