ARILLUS, ALBUMEN. 809 



the pulp of the berry consists of these fleshy arils, much com- 

 pacted. (Fig. G77, G78.) 



598. The laciniate aril of the nutmeg (mace) and, it is said, 

 the bright red and pulp}' aril of Euonymus and Celastrus begin 

 in the manner of a ca- 

 runcle, and are formed 



(mainly if not wholly) 



of an outgrowth at or 



around the micropyle. So 



that, if an orthotropous 



seed ever developed an 



aril of this sort, it would 6-7 ers 



be seen to begin at the apex of the seed and cover it from above 



downward. Planchon, who distinguished this from the true aril, 



gave to it the name of ARILLODE (Arittodiuni) or False Arillus. 



599. The Nucleus, or kernel of the seed, consists of the Albu- 

 men, when this substance is present, and the Embryo. 



600. The Albumen, as described in the second chapter (25, &c.) , 

 is the name generally employed b} T s}'stematic botanists for a 

 store of nutritive matter in the seed outside of the embryo, 

 whatever its chemical composition. It is not here the name 

 of a chemical substance (albumen or albumin), but of a cellular 

 structure, the cells of which arc loaded commonly with starch- 

 grains (as in the Cerealia), more or less mingled with other 

 matters, or else filled with an encrusting deposit of some equiva- 

 lent substance, as in the cocoanut, coffee-grain, &c. The cells 

 in which this deposit is made belong either to the original tissue 

 of the nucleus, or to a new formation within the embryo-sac, 

 mostly to the latter. (503.) 



601. Albumen ma}- be said to belong to all seeds in the grow- 

 ing stage. In what are called albuminous seeds it persists and 

 forms either almost the whole kernel, the embryo remaining 

 minute (as in Fig. '23, 54, 680), or forms a large portion of it (Fig. 

 13, 17, 19, 21, 48, 663, 664), or, by the growth of the embryo 

 displacing it, it may in the ripe seed be reduced to a thin stratum 

 or mere lining to the contiguous seed-coat ; or it ina}- disappear 

 altogether, as in the seeds of Maple, Almond, Squash, Pea, and 

 the like, which are therefore said to be exalbuminoits. The 

 difference between albuminous and exalbuminous seeds is that 

 the maternal nutritive deposit is transferred to the embryo in 



FIG. 677. Section of pericarp and placenta of Podophyllum peltatnm; the pulp of 

 the latter mainly of the nature of arillus. investing the seeds. 678. The arillus of one 

 seed detached and enlarged, divided lengthwise, showing the seed within. 



