Chap. II. EUPTUEE OF THE SEED-COATS. 103 



ing oif of the seed-coats would be sufficient to account 

 for the development of the peg. Yet, according to 

 IE. Flahault, seedlings which have been preventeil 

 from casting their seed-coats whilst beneath the 

 ground, are inferior to those which have emerged with 

 their cotyledons naked and ready to act. 



The peg is developed with extraordinary rapidity . 

 for it could only just be distinguished in two seed- 

 lings, having radicles -So inch in length, but after an 

 interval of only 24 hours was well developed in 

 both. It is formed, according to Flahault, by the 

 enlargement of the layers of the cortical parenchyma 

 at the base of the hypocotyl. If, however, we judge 

 by the effects of a solution of permanganate of 

 potassium, it is developed on the exact line of 

 junction between the hypocotyl and radicle; for 

 the flat lower surface, as well as the edges, were 

 coloured brown like the radicle; whilst the upper 

 slightly ilielined surface was left uncoloured like the 

 hypocotyl, excepting indeed in one out of 33 im- 

 mersed seedlings in which a large part of the upper sur- 

 face was coloured brown. Secondary roots sometimes 

 spring from the lower surface of the peg, which thus 

 seems in all respects to partake of the nature of the 

 radicle. The peg is always developed on the side which 

 becomes concave by the arching of the hypocotyl: 

 and it would be of no service if it were formed on any 

 other side. It is also always developed \^■ith the flat 

 lower side, which, as just stated, forms a part of the 

 radicle, at right angles to it, and in a horizontal plane. 

 This fact was clearly shown by burying some of the 

 thin flat seeds in the same position as in Fig. 62, 

 excepting that they were not laid on their flat broad 

 sides, but with one edge downwards. Nine seeds 

 were thus planted, and the peg was developed in the 



