PHYSIOLOGICAL BOTANY. 291 



After the fall of the petals and stamens, the nucleus 

 grows somewhat : a protuberance is then formed at the 

 margin of the exostome, which grows out, expands into a 

 membranous margin, and extending towards the base of 

 the nucleus, forms a hemispherical cover, which covers the 

 base of the nucleus, but leaves the micropyle completely 

 uncovered, whilst, on the other hand, the true aril covers 

 the micropyle. The author calls the aril of Euonymus a 

 false aril or arillode. The definitions then of these parts 

 are : the true aril is an accessory covering of the nucleus, 

 which is developed around the umbilical aperture (hilum), 

 in the same manner as the proper coverings, and either 

 covers the exostome, or would do so if it were sufficiently 

 developed. The false aril or arillode is an expansion of 

 the margins of the exostome, which is reflected around 

 this aperture, but always leaves it uncovered. We have 

 examples of true arils in the Dilleniacese, the Samydaceae, 

 the Bixinese, Nymphcea ccerulea and alba, but it is absent 

 in Nuphar lutea. Moreover, Chamissoa is mentioned as 

 an example, and a description is then given of the seed 

 of Cytinus Hypocistis. The ovary of this plant is filled 

 with a mucus, and upon its walls there are ramified but 

 compactly superimposed placentae. I shall give the descrip- 

 tion of the ovule and seeds in his own words : " Ovula 

 ortholropa, creberrima, minutissima, occidua, utrinque at- 

 tenuata, basi arillata. Integ. unicum, vasculis destitutum, 

 arete adhcerens, membranaceum, pellucidum, apice perfora- 

 tum. Nucleus solidus, cellulosus, ovulo conformis, subdia- 

 phanus. Arillus irregulariter cupuliformis, brevis, crassus, 

 margins incequalis e cellulis laxis latis constans, vix quar- 

 tam ovuli partem inferiorem oUegens, ab eodem facillime 

 secedens. Semina (in fructu siccato) ovulis conformia, 

 pallide lutea, mucilagine in lacrymas solidas, vitreas co- 

 agulata involuta. Arillus et integumentum ut in ovulo, 

 prior won raro obliterates. Nucleus solidus, omnino eel- 

 lulosus. Embryo nullus." The author in fact thinks, that 

 no embryo is present, because as the ovule is orthotropous, 

 impregnation could only occur through the mucus of the 



