490 OX SEEDLINGS 



pendulous?, anatropous or shortly amphitropous ; the micropyle 

 is always superior. The fruit is one-seeded, indehiscent, and 

 generally small, sometimes an achene and dry, fleshy or succu- 

 lent, free or included in, or adnate to the perianth ; sometimes 

 it is a drupe and free, or it consists of numerous carpels, im- 

 mersed or sunk in a fleshy receptacle or surrounding the thala- 

 mus and densely aggregated or united, forming a compound 

 fruit as in the Mulberry. The seed is erect, pendulous or late- 

 rally attached and conforms to the cavity of the fruit ; the testa 

 is membranous or rarely crustaceons. Endosperm is wanting 

 or forms a thin layer surrounding the embryo, and occupying 

 its sinus in some cases when it is sometimes unilateral. The 

 embryo is straight or curved, and fleshy with a short or minute, 

 superior radicle. Sometimes the cotyledons are variously 

 unequal, folded, or involute, with a superior radicle, or the 

 latter is again curved downwards and incumbent. 



Exceptional cases occur where endosperm is copious and 

 fleshy, as in a few species of Trema, in Parasponia, in the 

 tribe Cannabineae, in Morus, Bosquiea, Sceptrocnide, Parie- 

 taria, Urtica dioica, Cypholophus, Thelygonum,. and in a few 

 species of other genera. 



One of the simplest types of embryo is that occurring in 

 Parietaria officinalis. The seed closely conforms to the ovoid 

 fruit and contains a large quantity of endosperm surrounding 

 the straight embryo, which has oval cotyledons, longer than 

 the radicle. The achene of Urtica dioica (fig. 650) is ovoid 

 and laterally compressed with a smaller quantity of endosperm 

 surrounding the embryo. The cotyledons are orbicular, emar- 

 ginate owing to a thickening at the chalaza, and longer than 

 the radicle. 



A distinct type occurs in Caanabis sativa where the achene 

 is oval and the seed which conforms to it has a small quantity 

 of endosperm between the radicle and the oval, plano-convex, 

 incumbent cotyledons. 



A still more complicated type is met with in Celtis occiden- 

 talis. The fruit is a somewhat fleshy drupe, one- or sometimes 

 two- seeded, with a bony endocarp. The seed is campylotropous, 

 inserted near the top of the cavity, and when two are present, 

 they are collateral. The endosperm occupies a small space 



