MORPHOLOGY OF THE BAELEY GRAIN. 



aJly proceeds from the glumes inward. The glumes, the seed coat of the 

 caryopsis, and the seed proper, each consists of several kinds of tissue. 



THE GLUMES. 



The outer surface of the glume is protected by a heavy cuticle. 

 The cuticularization does not penetrate deeper than the first row of 

 cells. The three outer layers of cells have heavily reinforced (scler- 

 enchymal) walls, while the underlying layers are thin walled and more 

 variable. They are usually three or four in number. The vascular 

 bundles of the glume are normal leaf bundles 



THE SEED COAT OF THE CARYOPSIS. 



The term ''seed coat of the caryopsis" is here used to include 

 groups of tissues from three separate origins: The pericarp, the 

 testa, and the semipermeable 

 membrane. The pericarp is the 

 remains of the ovary waU. Its 

 outer layer hes flat against the 

 glume and is united with it. 

 Beneath the layer in contact with 

 the glume are several layers of 

 parenchyma, consisting of much 

 flattened and often almost dis- 

 connected cells. Below this arc 

 two layers of parenchyma that 

 formerly contained chlorophyll. 

 Though equally flattened through 

 pressure, they arc in much better 

 condition as a layer. The cells 

 of this tissue are abnost at riglil 

 angles to those of the main pa- 

 renchyma region and tangential 

 to the grain. On the inside of 

 the pericarp are sometimes found 

 scattering fragments of the inner epidermis of the ovary, their cells 

 also elongated lengthwise with the grain. 



The testa is the remnant of the inner of the two integuments that 

 once existed inside the ovary wall, tlui outer one ha\dng disa])pear<>(l. 

 The cells of the testa are crushed almost to the point of disa])])earance, 

 being repr(^s(!nte(i in the rijx'ned grain })y a Jiiereline. In intiinat(MU)n- 

 tact with the testa and much better preserved is the inv(!sting mem- 

 brane of the nucellus. It consists of moderately thickened ('(dlsflatlcned 

 by pressure. On th(! inside of this ureocciisionjil ])iilcii('s of j)ai'tly iciib- 

 sorb(!d cell walls, remnants of the niiccllai- lis:^iic. AccorditigtoBrown,' 

 the investing membrane of \]]o rniccJhis pi-ohably roiins t he s(>mi])erme- 

 abl(! menibrane, though the iiUKM" intcgninent may also be concerned. 



■ Brown, A. J. On the exlMtenne ofn Hnmlpormpuhle mombrano Inclosing the iieods of itomo of the Urani' 

 Inesc. Annah of IJolany , v. 21 , no. 81 , p. 7B-87, 1907. 



Fig. 1. 



.V grain of '2-rowcd barley: A, norsal view; 

 B, ventral view. 



