354 ON SEEDLINGS 



either side. A. campestre, A. austriacum, A. platanoides, and 

 A. Lobelii agree pretty closely with this type, except that the 

 last-named undergoes a considerable amount of longitudinal 

 folding or plaiting. 



A. dasycarpum seems to constitute a fifth type, but only 

 dried herbarium specimens were examined. The seed-vessel 

 is laterally flattened, with the seed conforming to the interior. 

 The embryo originates like all the foregoing, and during 

 its development it becomes twisted round, so that the coty- 

 ledons place themselves in the broad plane of the seed with 

 their edges vertical; but they are flat, as shown in trans- 

 verse section, and often oblique or not exactly opposite one 

 another, or the tip is, sometimes at least, again reversed 

 from the hilum towards the end of the seed away from the 

 placenta. 



The sixth type is shown in A. circinatum. The seed- 

 vessel is tumid, not indented, and the oblong seed conforms 

 to the interior. The curved portion of the seed containing 

 the radicle is inferior, or in other seeds is twisted round 

 to the side, rising obliquely, and in some cases is lateral 

 or in others almost or quite superior. The raphe is in this 

 case often lateral or inferior, passing round the lower instead 

 of the upper side of the seed. The cotyledons have their 

 edges vertical, with their backs to the radicle (incumbent), and 

 are more or less transversely biplicate. The folds are less 

 regular or compact than in A. Pseudo-Platanus, owing to the 

 greater length and different shape of the seed, which conforms 

 to the cavity containing it. 



Seedlings. There is considerable variety in this extensive 

 Order ; but the seedlings coming, under my notice may be 

 classed into three distinct groups, namely, those where the 

 cotyledons become aerial and more or less foliaceous, those 

 where they are subterranean, and those where they are aerial 

 but do not leave the testa. 



The strictly aerial kinds exhibit four or more forms. 

 The cotyledons of Cardiospermum Halicacabum (fig. 250) 

 are small, oblong, truncate, and very caducous, which may 

 be ascribed to their character and mode of folding in the 

 seed. The fact of their falling early points to their losing 



