414 TRANSACTIONS AND PROCEEDINGS OF THE [Sess. lix. 



The whole seed is yellow or light yellow-brown in colour, 

 with a smooth but not shining surface. 



The small, point-like, hilum scar is situated in the hollow 

 formed by the projection of the apex of the radicle, while 

 on the end of the seed, beyond the hilum scar, is a small 

 patch darker brown in colour than the rest of the seed. 



Size, 2*75 mm. long X 2 mm. broad, including the 

 radicle, x 1*5 mm. thick; or, according to Hartz, 

 2*2 X 1'5 X 1 mm. 



Germination. — During the earlier stages of germination 

 the rapid elongation of the hypocotyl carries the young 

 crowing root out of the seed in a downward direction, 

 forcing it into the soil, and when the root itself has 

 reached a length of about 4-5 mm., the hypocotyl is at 

 least twice as long, and the seed still below the surface of 

 the soil. At about this time, however, the formation of 

 the first root hairs may be observed taking place near the 

 point of junction of the root and hypocotyl These soon 

 attach themselves to particles of soil, and so anchor that 

 particular part of the compound radicle that any further 

 progress made by the root in the soil must be due to its 

 own elongation. The hypocotyl, however, still continues 

 to grow, and, as its lower end is now fixed, this increase in 

 length has the effect of withdrawing the cotyledons from 

 the seed-coat, which is retained below the surface by the 

 weight of the superincumbent soil, while the liberation 

 of the cotyledons is facilitated by the presence of the 

 mucilaginous endosperm. 



In a normal germination, the first part of the embryo to 

 appear above the surface of the soil is the bent upper part 

 of the hypocotyl, followed at once by the bases of the 

 cotyledons. As soon as these last are free from the soil a 

 backward curvature of the hypocotyl takes place, the still 

 closed cotyledons are swung round in a vertical plane till 

 the erect position is reached, then each curves outwards 

 laterally till it reaches its permanent horizontal position. 



Cotyledons. — The petiole is rather short, and the 

 lamina is attached to its apex by a short slightly swollen 

 joint. The lamina is, in general, expanded almost 

 horizontally, and may even droop somewhat at its apex, 

 while the petiole, on the other hand, is nearly, if not quite 



