TRITICUM 149 



tissue. One large and two smaller vascular bundles are present, 

 the former being continuous with the midrib of the glume. 



Opposite to and enclosed by the lemma, with its abaxial surface 

 toward the rachilla, is the palea, which is diverged from a very 

 short pedicel or flower stalk. (Fig. 61, C) This is an awnless, 

 two-keeled bract of thinner texture than the lemma, having trans- 

 parent, infolded margins. Enclosed by it are the three stamens and 

 single pistil, as well as two small, ovate, membranous scales, called 

 the lodicules, which lie on the opposite side of the pedicel from the 

 palea and near the base of the ovary. The large anthers are sagit- 

 tate, and the cylindrical filaments have a single vascular strand. 

 The ovary is one-celled, covered with down at its apex, and sur- 

 mounted by two short styles which terminate in feathery, brush- 

 like, stigmatic branches. 



At anthesis, the swelling of the lodicules results in the pushing 

 apart of the lemma and palea; and the filaments elongate rapidly, 

 carrying the anthers up and outside of the glume. Dehiscence 

 begins before the flowers are fully open, continuing until they again 

 close; and, in most wheats, close pollination occurs although there 

 may be a small percentage of natural crossing. The latter is 

 commonly the case in durum wheat. 



ANATOMY 



The Mature Grain. — The mature grain or fruit is a caryopsis. 

 The pericarp and the remains of the integuments of the single seed 

 are so closely adherent that they cannot be readily separated from 

 each other at maturity. The grain is ovate with a furrow or crease 

 on the surface facing the palea which is caused by an infolding of 

 the lateral portions as maturation and desiccation proceed. The 

 surface of the grain is smooth except at the stigmatic end, where 

 there is a brush or tuft of persistent hairs. These become thick- 

 walled and rigid surrounding the styles which may sometimes 

 persist. (Fig. 6i.) The embryo develops at the base of the fruit 

 on the side away from the groove, and may be located externally 

 by the wrinkled surface of that portion of the pericarp which 

 overlies it. 



The histology of the grain has been investigated by Bessey (x), 

 Percival (10), Tschirch and Oesterle (14), Winton (16), and others. 

 It may be divided into three main regions: (i) the bran layer 

 including the pericarp, remains of the seed coat and nucellus; 



