352 ON SEEDLINGS 



separable with difficulty when mature. The latter are petio- 

 late; the two-leaved plumule is well developed, and the large 

 conical radicle lies in a separate cavity in the thick testa. 

 Spiny indehiscent fruits consisting of one to three globose, free 

 or connate cocci occur in some species of Nepheliurn, and 

 N. Litchi, having a crustaceous, brittle, tuberculated pericarp 

 and a pulpy, edible aril, is often met with in British fruit 

 markets. The embryo is fleshy, and the cotyledons plano- 

 convex. 



Fleshy indehiscent fruits are met with in Sapindus and 

 others, while those of Spanoghea are fleshy, but burst open 

 transversely. Those of Melicocca, Lecaniodiscus, and Lepi- 

 santhes are drupaceous and indehiscent. The fruits of 

 Euphoria and Schmidelia break up into indehiscent cocci, 

 while the cocci of Diplopeltis are dehiscent. Triangled and 

 trilobed fruits are very frequent , but those of Bridgesia and 

 Paullinia are three- winged. 



Samaroid fruits are not unusual, and, although not typical 

 of the Order, are frequent and important. Bridgesia, Urvillea, 

 Toulicia, Serjania, Thouinia, and Atalaya have fruits consist- 

 ing of three samaras, while those of Acer and Negundo 

 have only two. With exception of Thouinia, all are inde- 

 hiscent. 



The species of Acer l may be grouped into five or six very 

 distinct types according to the form of the fruit, seed, and 

 embryo, but more particularly of the latter. The ovules are 

 eampylotropous in all cases, with the micropyle inferior, 

 except in A. circinatum, where it is variable, ascending or 

 horizontal, with the raphe ventral, and ascending more or less 

 along the upper edge or surface. 



The first type may be represented by A. Pseudo-Platanus. 

 The seed-vessel is tumid on both surfaces, and the seed 

 ovoid, slightly compressed laterally. The embryo commences 

 by coiling round the circumference of the seed, but the 

 cotyledons finally become transversely twice folded with 

 their backs to the placenta and the incumbent radicle in 

 the lower part of the seed. In rare cases the cotyledons 



1 See an interesting memoir on this group by Pax, Engler's Bol. Jahrb. 

 1885. 



