COTYLEDONS. 



611 



particles of soil by means of abundant root-hairs. The hypocotyl also, into which 

 the root merges, grows at first downwards into the earth, but of course only for a 

 short time, for this is very soon altered ; and growth then takes place in an opposite 

 direction towards the light, and immediately after this alteration of direction the 

 withdrawal of the cotyledons commences. It follows from what has been said that 

 the hypocotyl is fixed both above and below — below by the root which has grown 



Fig. 145.— Liberation of the Cotyledons from the cavity of the seed or fruit husk. 



» Gourd (Cucurbita Pepo). 2 Asafoetida {Scorodosma Asa foetida). 3 Immortelle (Helichrysian annuuin). ■« Cross-section 

 through the cotyledons, showing them curled up in the pericarp of the Immortelle. « Cardopatium corymbosum (after 

 Klebs). Fig. 1-3, natural size ; fig. 4-5, somewhat enlarged. 



firmly into the ground, above by the firmly glued seed-covering in which che 

 cotyledons lie. As soon as it increases in length it forms a well-marked arch, 

 frequently even a loop, with the convex side turned upwards (c/. fig. 145^). 

 Naturally it thus exercises a severe strain on both ends. The root, well planted in 

 the earth, can no longer be disturbed from its position, but the effects of the tension 

 make themselves felt on the cotyledons, which still lie in the seed. The coat of the 

 Gourd seed bursts, the cotyledons are drawn out from the yawning cleft, the 

 hypocotyl straightens itself, and the two cotyledons separating from each other 

 turn their upper sides towards the light (fig. 145 ^, on the left). 



