154 



MOEPHOLOGY, OE COMPAEATIYE ANATOMY. 



are liable to be mistaken for seeds when detached ; they are known by 

 the remains of the style, and by the complete seed with" its proper coat 

 being distinguishable on opening the pericarp (tig. 313). 



Fig. 313. 



Fig. 314. 



Fig. 315. 



Fig. 316. 



"Pig. 313. Vertical section of an achaenium of Ranunculus, showing the seed within the peri- 

 carp and with a minute embryo in the albumen. 



Fig. 314. Section of the seed of Typha, showing the straight embryo in the axis of the peri- 

 sperm or albumen. 



Fig. 315. Section of the caryopsis of Wheat, showing the abundant perisperm, a, with the 

 embryo, b, at the base, outside. 



Fig. 316. Section of the seed of Iris, with the embryo enclosed in the perisperm. 



Enations from the Seed. A. considerable number of seeds 

 possess a coat or appendage distinct from the proper integument, 

 and produced entirely during the development of the seed from the 

 ovule that is to say, after the fertilization of the latter. These 

 additional structures are frequently fleshy when mature, as in the 

 Spindle-tree, Euonymus, Podophyllum, &c. The older authors 

 called all the forms by the same term, arillus ; recent authors 

 distinguish the true arillus, which grows up over the seed from 

 the funiculus, like the primine and secundine, as in Nymplicea, 

 Passion-flowers, &c., from the arillode, which originates at or near 

 the micropyle, and grows down more or less over the testa, as in 

 Euonymus (where it forms a pulpy coat), in Euphorbia, Ricinus 

 (fig. 311), Polygala, Ac. 



The mace of the nutmeg is an arillus, adhering both to the hilum and 

 micropyle. 



The appendages which grow from the raphe, in Chelidonium, Asanim, 

 Viola, &c v are sometimes called strophioles. 



The body of the seed is composed either of the embryo alone, or 

 of the embryo imbedded in a mass of tissue, called the perisperm, 

 or albumen (figs. 313-320). Seeds wherein the embryo is immedi- 

 ately invested by the integuments are commonly called eocalbu- 

 minous or aperispermic (figs. 321 & 323). Where perisperm exists, 

 they are called albuminous (figs. 313 &c.). 



The term albumen, founded upon the functional analogy with the albu- 

 men or white of an egg, is very inconvenient, as it has a distinct chemical 

 sense, in which it is frequently used in the chemical questions of vegetable 



