318 ON SEEDLINGS 



the cotyledons in Euta, with a reniform seed, and very short 

 in Citrus and Dictamnus with obovoid seeds. 



A very abnormal condition prevails in the seed of the 

 Orange (Citrus Aurantium). Each contains from two to four 

 embryos sufficiently developed to germinate and grow into 

 plants, besides a similar or even greater number of very small 

 ones that are unable to germinate. The large ones are 

 fleshy, colourless, and nearly always have very unequal cotyle- 

 dons of various shapes owing to mutual compression. There 

 is usually one large cotyledon in each seed, belonging probably 

 to the true embryo, while all the rest are smaller, and packed 

 on to the face of the large one, completely filling the seed. 

 The large cotyledon is often deeply concave with the others 

 packed into the cavity. Strasburger states that the super- 

 numerary embryos are developed by prolification from the 

 tissue of the nucellus bordering on the embryo-sac. 



A similar case occurs in Triphasia trifoliata, and is pro- 

 bably due to the same cause. The seed is exalbuminous as 

 in the Orange, and generally contains two embryos of different 

 sizes, with usually very unequal cotyledons. The larger cotyle- 

 don is concavo-convex or in some cases infolded at the sides. 

 Three embryos are also not unusual, when one or other of the 

 cotyledons is infolded and often more or less deeply lobed. 

 This is due sometimes to one cotyledon becoming folded over 

 the edge of the other. 



Seedlings. The seedlings I have met with all belong to 

 the shrubby or arboreal types of Butacefe. Amongst them 

 two leading types of cotyledons may be observed, namely, an 

 aerial and a subterranean one. Those of Correa Colvillei are 

 lanceolate, one-nerved, and taper to a very short petiole. The 

 cotyledons of C. viridiflora differ in being narrower and linear- 

 oblong. Ptelea trifoliata has more foliaceous, unequally 

 oblong, finely crenulate cotyledons. Those of P. aptera differ 

 in being proportionately longer and oblong-lanceolate. In 

 Limonia acidissima we have a type that is intermediate between 

 those having strictly aerial and strictly subterranean cotyle- 

 dons. Although they are carried to a considerable height 

 above the soil they are fleshy, pale green, and fall away 

 early. Their function is evidently to constitute a storehouse 



