340 ORGANOGRAPHY. 



The endopleura is generally of a soft and delicate nature, 

 although sometimes of a fleshy character, either entirely or in 

 part. It is usually of a whitish colour, and more or less trans- 

 parent. This layer is closely applied to the nucleus of the 

 seed, which it accompanies in all its foldings and windings; and 

 in some cases even dips down into the albumen of the nucleus^ 

 and thus divides it more or less completely into a number 

 of parts, as in the Nutmeg, Betel-nut {fig. 740, p), &c. ; the 

 albumen is then said to be ruminated. (See Albumen, p. 344.) 



The testa may either accompany the endopleura in its wind- 

 ings ; or, as more frequently happens, especially Avhen the 

 nucleus is curved, the endopleura only follows the nucleus, the 

 testa remaining in an almost even condition. 



Arillus. — Besides the two integuments described above, as 

 being usually found in all seeds; we occasionally find on the 

 sm-face of others, an additional integument, usually of a partial 

 nature {fiy. 734, a, a), to which the name of arillus or aril has 

 been given. No trace of this is present in the ovule till after 

 the process of fertilization has taken place. Two forms of the 

 arillus have been described by St. Hilaire and Planchon, which 

 have an entirely different origin, the former being called the 

 true arillus, and the latter the false arillus or arillude. The true 

 arillus arises in a somewhat similar mannei* to the coats of the 

 ovule already described, that is to say, it makes its first ap- 

 pearance around the hilum in the form of an annular process 

 derived from the placenta or funiculus ; this gradually pro- 

 ceeds upwards, so as to produce a more or less complete ad- 

 ditional covering to the seed, on the outside of the testa. This 

 arillus is well seen in the Nymphcea {fig. 734, a, a), and Passi- 

 flora. 



The false arillus or arillode, according to the investigations 

 of St. Hilaire, and the more recent elaborate ones of Dr. 

 Planchon, arises from the micropyle, and seems to be a develop- 

 ment or expansion of the exostome, which gradually extends 

 itself over the testa to which it forms a covering, and after thus 

 coating the seed, it may lie even bent back again so as to enclose 

 the micropyle. The gradual development of the arillode in the 

 Spindle-tree {Euojiymus), is well shown in fig. 735. In the 

 Nutmeg, the arillode forms a scarlet covering to the testa, which 

 .is commonly known under the name of mace. Mr. Miers has 

 endeavoured to show, that the arillode in the Euonymus is pro- 

 duced from the funiculus rather than from the exostome of 

 the primine, in which case the arillode would necessarily be 

 of the same nature as the arillus. 



Carunclis or Strophioles. — These are small irregular pro- 

 tuberances which occur on various parts of the testa. They 

 are always developed, like the arillus and arillode, subsequent 

 to fertihzation, and arc accordingly not found in the ovule. In 



