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 itself whilst forcing a passage through the soil.

* ‘Botanical Text-Book,’ 1879, p. 22. [page 81]

Megarrhiza Californica.—­The cotyledons of this Gourd never free themselves from the seed-coats and are hypogean.  Their petioles are completely confluent, forming a tube which terminates downwards in a little solid point, consisting of a minute radicle and hypocotyl, with the likewise minute plumule enclosed within the base of the tube.  This structure was well exhibited in an abnormal specimen, in which one of the two cotyledons failed to produce a petiole, whilst the other produced one consisting of an open semicylinder ending in a sharp point, formed of the parts just described.  As soon as the confluent petioles protrude from the seed they bend down, as they are strongly geotropic, and penetrate the ground.  The seed itself retains its original position, either on the surface or buried at some depth, as the case may be.  If, however, the point of the confluent petioles meets with some obstacle in the soil, as appears to have occurred with the seedlings described and figured by Asa Gray,* the cotyledons are lifted up above the ground.  The petioles are clothed with root-hairs like those on a true radicle, and they likewise resemble radicles in becoming brown when immersed in a solution of permanganate of potassium.  Our seeds were subjected to a high temperature, and in the course of three or four days the petioles penetrated the soil perpendicularly to a depth of from 2 to 2 ½ inches; and not until then did the true radicle begin to grow.  In one specimen which was closely observed, the petioles in 7 days after their first protrusion attained a length of 2 ½ inches, and the radicle by this time had also become well developed.  The plumule, still enclosed within the tube, was now

* ‘American Journal of Science,’ vol. xiv. 1877, p. 21. [page 82]

.3 inch in length, and was quite straight; but from having increased in thickness 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 ½ inches of superincumbent soil, still retaining its arched form.  After reaching the surface it straightened itself in the usual manner.  In the accompanying figure (Fig. 58, A) we have a sketch of a seedling in this advanced state of development; the surface of the ground being represented by the line G...........G.