376 



SIR J. liTTBBOCK: PnYTOBIOLOOICAL OBSKRYATIOXS. 



they are petiolate when they take their origin close to 



the 



ground. There are no doubt some exceptions ; for instance, 



Fig. 02 



Fig. 93, 



Fig, 92. Seedling of JJt^onia lachiiom. Half nat. size. 

 Fig. 93. Seedling of ^, dloica, Nat. size. 



in some Bpeeles of IleJi/santm the cotyledons are radical and 

 yet sessile- I have, however, often in Algeria 



seedlings of 



this group in hot exposed Ksituations, where they "held the field" 

 alone, and being sure of ample heat and light, did not require to 

 be raised above tlie surface. 



The opposite exception is perhaps more common — /. e- when 

 the cotyledons, though raised, are still petiolate. Here, however, 

 tiie cotyledons are probably petiolate for the same reason as 

 the leaves — viz., when the foliage is large, leaf-stalks are an 

 advantage in carrying the lower leaves out of the shadow oi 

 those immediately above them. 



In another species of I)_elj)hinium {D. nudicaule^ fig. 32) the 

 cotyledons are raised well above the surface of the ground on astern 

 consisting of their own two stalks or petioles, which are connate, 

 though readily sej^arable from one another. Connate cotyledons 



