82 



HYPOCOTYLS, EPICOTYLS, ETC., Chap. II 



Fig. Sa, A. 



•3 inch in length, and was quite straight ; but from 

 having increased in thickr,ess it had just begun to 

 split open the lower part of the petioles on one side, 

 along the line of their confluence. By the following 

 morning the upper part of the plumule had arched 

 itself into a right angle, and the 

 convex side or elbow had thus been 

 forced out through the slit. Here 

 then the arching of the plumule 

 plays the same part as in the case of 

 the petioles of the Delphinium. As 

 the plumule continued to grow, the 

 tip became more arched, and in 

 the course 'of six days it emerged 

 through the 2^ inches of superin- 

 cumbent soil, still retaining its 

 arched form. After reaching the 

 surface it straightened itself in the 

 usual manner. In the accompany- 

 ing figure (Fig. 58, A) we have a 

 sketch of a seedling in this ad- 

 vanced state of development; the 

 surface of the ground being re- 

 presented by the line G G. 



The germination of the seeds in 

 one-haif their native Californian home pro- 

 ceeds in a rather different manner, 

 as we infer from an interesting 

 letter from Mr. Eattan, sent to us 

 by Prof. Asa Gray. The petioles 

 protrude from the seeds soon after 

 the autumnal rains, and penetrate the ground, generally 

 in a vertical direction, to a depth of from 4 to even 

 6 inches. They were found in this state by Mr. 

 Rattan during the Christmas vacation, with the plu- 



Megarrhiza Californica ; 

 sketch of. seedling, 

 copied from Asa Gray, 

 reduced to 

 scale : t-', cotyledons 

 within seed-coats ; /), 

 the two confluent 

 petioles ; h and r, hy- 

 pocolyl and radicle ; 



pi, plumule; ff G, 



surface of soil. 



