80 HYPOCOTYLS, EPICOTFLS, ETC., Chap. rt. 



either had proved decidedly advantageous or disad- 

 vantageous, one of them no doubt would soon have 

 prevailed. 



Asa Gray has described * the peculiar manner of ger- 

 mination of three widely different plants, in which the 

 hypocotyl is hardly at all developed. These were there- 

 fore observed by us in relation to our present subject. 



Delphinium mdieaule. — The elongated petioles of 

 the two cotyledons are confluent (as are sometimes 

 their blades at the base), and they break through the 

 ground as an arch. They thus resemble in a most 

 deceptive manner a hypocotyl. At first they are 

 solid, but after a time become tubular ; and the basal 

 part beneath the ground is enlarged into a hollow 

 chamber, within which the young leaves are developed 

 without any prominent plumule. Externally root- 

 hairs are formed on the confluent petioles, either a 

 little above, or on a level with, the plumule. The 

 first leaf at an early period of its growth and whilst 

 within the chamber is quite straight, but the petiole 

 soon becomes arched ; and the swelling of this part 

 (and probably of the blade) splits open one side of 

 the chamber, and the leaf then emerges. The slit 

 was found in one case to be 3'2 mm. in length, and 

 it is seated on the line of confluence of the two 

 petioles. The leaf when it first escapes from the 

 chamber is buried beneath the ground, and now an 

 upper part of the petiole near the blade becomes 

 arched in the usual manner. The second leaf comes 

 out of the slit either straight or somewhat arched, but 

 afterwards the upper part of the petiole, — certainly in 

 some, and we believe in all cases, — arches itseK whilst 

 forcing a passage through the soil. 



' Botanical Text-Book,' 1879, p. 22. 



