ANATOMY AND PHYSIOLOGY OF PLANTS. 243 



27. The umbilical cord is the small peduncle or stalk 

 by which a seed is attached to the pericarp or seed- 

 vessel. 



It is through the umbelical cord the vessels are supposed to pass 

 to nourish the seed, for there are no seeds without it. 



28. The hilum or eye is the external mark or scar, 

 formed by the breaking off or separation of the stalk or 

 umbilical cord. 



29. The seed-coat is the external covering, and ac- 

 cording to its situation, it is said to be either an exterior 

 or interior integument. 



These integuments, are sometimes however, enveloped by an 

 additional covering called the pellicle or seminal epidermis. 



30. The exterior integument or testa, is the original 

 cuticle of the nucleus, not easily separable in the early 

 stages of its growth, but detachable when the fruit is 

 ripe, when it is generally of a membranous or leathery 

 texture ; though sometimes soft and fleshy, and some- 

 times crustaceous and bony. 



When a seed is furnished with two proper coats, the testa or shell 

 is the outer one : when there is only one coat, this is accounted the 

 shell ; and when there are more than two coverings, the second from 

 the nucleus is named the shell. 



31. The use of the testa or shell is, to contain and 

 give form to the kernel or seed. 



It is deemed an essential part of the seed, because the kernel, 

 which originally was wholly fluid, could not have been formed unless 

 a coat had been placed round it. it is a part, also, never wanting. 



