114 OEGANOGKAPHY AND GLOSSOLOGY. 



of the plant, lengthens during germination, the cotyledons are raised, and appear 

 above ground ; they are then said to be epigeal (c. epigcei, Kidney-bean, fig. 650 ; 

 Radish., Lime}. When the caulicte is very short, and the plumule (which forms the 

 second internbde) rapidly lengthens, the cotyledons remain in the ground, often even 

 within the seed-coats ; they are then said to be hypogeal (c. hypogcei, Spanish Kidney - 

 bean, Oak, Graminece, Orange, fig. 651). 



In monocotyledons, the evolution of the radicle presents a remarkable pecu- 

 liarity : it is provided at the base (fig. 642) with a sort of sheath, named the 

 coleorhiza ; this is nothing but an outer cellular layer which, having been unable to 

 accompany the development of the radicle (R), has been pierced by it. 



