HOW TO KNOW THE GRASSES 



are arranged in panicles, or two-rowed spikes, or one-sided spikes, or 



racemes. The parts of the inflorescence include the stalk or peduncle, 

 the central axis or rachis, main and small branches, and the stalks of 

 the individual spikelets or pedicels. At the base of each branch there 

 may be found a Uttle swelling, the pulvinus, which helps spread the 

 branch of the inflorescence when it emerges from the sheath. 



SPIKELETS 



Since the flowers of grasses are minute, simple, and very similar, 



they are rarely used in classification. Instead, we look for differences 



in the bracts (modified leaves) which surround the flowers. The unit 



subdivisions of the inflorescence are called spikelets (Fig. 6). The 



LEHHA 



2:GLUnE 



RACHILLA 



[FLORET 5^'^^^- 

 PALEA 



fGLUME 

 RACHILl 

 CALLU 



PEDICEL 



A\JN- 

 TOOTH- 



LEMMA 



5TAnEN5 



Figure 6 



simplest sort of spikelet is merely a tiny scaly branchlet of flowers, 

 each flower being surrounded by two bracts. At the base of this 

 branchlet there are two bracts which have no flowers in their axils. 

 These are the first and second glumes. The remainder of the spikelet 

 is made up of flowering units called florets, which are arranged alter- 

 nately in two rows on a central stalk, called a rachilla, which is usually 

 concealed by the overlapping florets. Each floret consists of an outer 

 bract or lemma and an inner bract or palea, with the naked flower 

 between them. The lemma corresponds to an ordinary foHage leaf, 

 the palea to the prophyllum, and the flower to a branch. During the 

 brief time of flowering, two little bUsters, the lodicules, which he be- 

 tween the ovary of the flower and the lemma, swell up and force the 

 lemma outwards. This allows the stigmas and stamens to protrude. 

 The lodicules are the evolutionary vestiges of a calyx. If you can find 

 smooth brome grass, orchard grass, or any one of many other grasses 

 in bloom in the morning dew, you can usually observe the lodicules 

 with a hand lens. The actual flower consists of two lodicules, three 

 stamens with long slender filaments, and cm ovary with two feathery 



