262 Inheritance of Glume Length and of Colour' in Oats 



The second 

 skin. 



The Girdle Cells. Very regular, delicate cells with ' 

 pitted lateral walls and long axes at right angles to 

 those of the components of the first skin. 



The Tube Cells, or Endocarp. Scattered vermiform 

 cells, often coalescing, running lengthwise in the grain. 

 They resemble later tubes and the longer the grain 

 the more conspicuous they are. They are always best 

 developed at the embryo end and on the side remote 

 from the groove. To them often adhere 



The Spermoderm and the Perisperm, two delicate 

 cell laminae which are not strictly pericarp, but the 

 outermost layers of the seed. 



The purple colour is found in the sap of the girdle cells, staining all 

 or part of it according to the distribution and intensity. The position 

 of this pigmentiferous layer is shown in Plate XIV, figs. 9 and 10, the 

 first of which shows it in a transverse section of the grain, and the 

 other in a superficial view of the girdle cells, more particularly where 

 they are not covered over by the fragment of epicarp. After immersion 

 in dilute sulphuric acid (1 in 20) for a short time, the grain turns 

 a deep crimson. This reaction, in conjunction with microscopical exami- 

 nation, has proved very useful in the detection of faint purple tinges 

 in grains which showed a slight streak to which the overlying portions 

 of the pericarp gave a doubtful, brownish appearance. For whereas 

 the acid produces a distinctive coloration, water causes the antho- 

 cyanin first to fade and then to become dull green, — a colour which 

 is much commoner than crimson, far less vivid, and by 

 distinctive. 



In both figures the acid reaction colour is illustrated. 



no means 



fl 



The F^ Generation. 



A type of ^1 ear is shown on Plate XIV, fig. 5. All the ears approxi- 

 mate to this type, of which the glumes are intermediate in shape and 

 size between those of the parents, though the fluctuations range from 

 glumes slightly longer than those of Eloboni to others a little shorter 

 than the minimum Polonicum glume. Plate XIV, fig. 6, illustrates these 

 two types (c and a) as well as the more general average (6). The grain 

 is also of intermediate dimensions, as will be seen fi-om Plate XIV, fig. 7, 

 m which it is placed between the parent grains for comparison. 



The ^1 grains were all purple. 



