TILIACE.E 277 



comparative size and complication is met with in the genus 

 Tilia itself, which may be taken as the type of a fourth group. 

 The ovary is five-celled with two ovules in each cell, but as it 

 matures into fruit, one seed generally takes the lead, outgrowing 

 all the others, which, together with four out of the five cells of 

 the ovary, remain small and get crushed on one side. The 

 fruit is an indehiscent nutlet, with one, rarely two seeds ; the 

 latter are obovoid or subglobose, deep brown, and have the 

 testa thickened at the chalaza. The endosperm is copious, 

 fleshy, pale yellow, or nearly white. The embryo is at first 

 obtusely ovate, with entire undivided cotyledons, which as 

 growth goes on become deltoid and subpalmately five-lobed. 

 When the apex comes in contact with the testa in the chalazal 

 region of the seed, the cot}iedons bend and then become folded 

 or doubled upon themselves with the loop of the fold sharply 

 deflected on the ventral aspect. The terminal lobe then grows 

 in the opposite direction, and curves round the apex of the 

 seed, with the tip so nearly exposed as to be quite visible 

 through the endosperm. The two pairs of lateral lobes reach 

 the sides of the seed, and become curved round it to the dorsal 

 aspect, where their tips also become quite visible through the 

 endosperm. The lobes are narrowly ovate, obtuse, and each 

 has a strong median nerve running through it ; the lower 

 pair springs from the base of the lamina, while the pair above 

 them arises from the side of the primary nerve ; the basal pair 

 and the terminal lobes are considerably larger and longer than 

 the middle pair. The hypocotyl and radicle are cylindrical and 

 obtuse or somewhat clavate. The above characters have been 

 taken from T. vulgaris (fig. 223, which shows the form of the 

 embryo separated from the endosperm). T. petiolaris differs 

 only in minute particulars ; a section of the fruit shows 

 (fig. 224) the relative position of the embryo and seed to the 

 fruit ; the embryo as a whole is less folded than in T. vulgaris. 

 The basal and terminal lobes of the cotyledons are shorter, 

 blunter, and more rounded, while the median pair is relatively 

 very small. The median nerve of the latter sometimes arises 

 from the base of the lamina, in which case the venation and 

 divisions are truly palmate. 



The folding of the various parts of the embryo is easily 



