CHAP. II, BREAKING THROUGH THE GROUND. 89 



plumules were developed in the axils of the petioles 

 of both cotyledons, and these were as perfectly arched 

 as the normal plumule ; yet they had not been sub- 

 jected to any confinement or pressure, for the seed- 

 coats were completely ruptured, and they grew in the 

 open air. This proves that the plumule has an innate 

 or spontaneous tendency to arch itself. 



In some other cases the hypocotyl or epicotyl pro- 

 trudes from the seed at first only slightly bowed ; but 

 the bowing afterwards increases independently of any 

 constraint. The arch is thus made narrow, with the 

 two legs, which are sometimes much elongated, parallel 

 and close together, and thus it becomes- well fitted 

 for breaking through the ground. 



With many kinds of plants, the radicle, whilst still 

 enclosed within the seed and likewise after its first pro- 

 trusion, lies in a straight line with the future hypocotyl 

 and with the longitudinal axis of the cotyledons. This 

 is the case with Cucurbita ovifera; nevertheless, in 

 whatever position the seeds were buried, the hypocotyl 

 always came up arched in one particular direction. 

 Seeds were planted in friable peat at a depth of about 

 an inch in a vertical position, with the end from which 

 the radicle protrudes downwards. Therefore all the 

 parts occupied the same relative positions which 

 they would ultimately hold after the seedlings had 

 risen clear above the surface. Notwithstanding this 

 fact, the hypocotyl arched itself; and as the arch 

 grew upwards through the peat, the buried seeds were 

 turned either upside down, or were laid horizontally, 

 being afterwards dragged above the ground. Ulti- 

 mately the hypocotyl straightened itself in the usual 

 manner; and now after all these movements the 

 several parts occupied the same position relatively to 

 one another and to the centre of the earth, which they 



