IX] " SEEDS " 157 



hairs on the lower part. 15x3 mm. Awn brown, 

 twisted and bent, arising from the middle, about 30 mm. 

 long. Caryopsis 7 mm. long, hairy at the top and 

 distinctly grooved. Rachilla with fine bristles. 



Avena pratensis, L. 



Palea very similar to A. fatua, apex 2 — 4-toothed or 

 bifid, rachilla with stiffer hairs. Caryopsis about 5 mm. 

 long. 



Avena pubescens, Huds. is a variety of A. pratensis 

 found on dry calcareous soils. The caryopsis is very 

 narrow, and the rachilla long and feathered with hairs. 

 "Seed" shorter than A. pratensis, 10 — 13mm., and 

 darker in colour. 



A. fatua is an excellent type of the grasses with dorsal twisted 

 and bent awns, and easily examined on account of its size. The 

 student will find diflioulties with other species of Avena and 

 Arrhenatherum. 



Harz says the stiff' hairs of Avena bring about the formation of 

 intestinal concretions (phytobezoars) and are therefore dangerous to. 

 domestic animals. 



** Palea TWt more than 7 — 10 mm. long. 

 t Caryopsis 4 — 5 mm. long. 

 Arrhenatherum avenaceum, Beauv. (Fig. 47). 

 Palese papery, ribbed. Awn 13 — 15 mm., twisted below ; 

 palese, with a tuft of hairs below and a ciliate keel, investing 

 the fruit : the whole being cylindrical, 8 — 10 mm. x 1"5. 



Caryopsis 4 — 5 mm. x 1-2, fusiform, pubescent. Ra- 

 chilla hairy. 



The distinctive difference between Avena and Arrhenatherum is 

 in the spikelets as a whole. The latter has the lower flower of each 

 spikelet male only. Samples contain the " double seeds," and the 

 awn of the upper fertile portion is short (see Fig. 69). 



