520 



WEED FLORA OF IOWA 



testa is but slightly developed. In some cases the underlying 

 parenchyma cells are not clearly defined. The blackish pigment is 

 found in the internal part of the palet; some also occurs in peri- 

 carps and the aleurone layer. The pericarp consists of one or 

 two rows of rather thin-walled, tangentially elongated cells. The 

 testa is reduced to a single layer of cells longer than broad. The 

 nucellus is nearly absent except in the groove. It consists of a 

 single row of thin-walled, colorless, compressed cells. In the groove 

 several rows of cells occur. The aleurone in the specimens studied 

 is made up of a single row of cells. The cells of the starch layer 

 are larger than those of the aleurone. 



Darnel (LoUum temulenhim L.). 



Dr. A. L. Winton describes its microscopic structure as follows : 

 The Flowering Glume is 6-8 mm. long, equaling or exceeding 

 the caryopsis. It is obscurely five-nerved, lobed at the end, and 

 bears an upwardly barbed awn often 15 mm. long. Like the glumes 

 of barley, oats, and other cereals, it consists of four coats, some of 

 which, however, are lacking on the margins and at the end. 1. The 

 Outer Epidermis differs greatly in structure in different parts of 

 the glume. At the margins (as is clearly shown in Fig. 1 by 

 Moeller*), it consists of straight-walled, elongated cells inter- 

 spersed here and there with short lance-shaped hairs. On the 

 greater part of the surface, however, the cells, as in barley and 

 some other cereals, are of three kinds : first, cells of wavy outline. 



FiQ. 398. Darnel (.Lolium temulentum) . Margin of flowering glume showing 



lance-sbaped hairs. X 300. 



(After Winton, Conn. Agr. Exp. Sta.) 



