GoRHAM, 071 the Umhellifercs. 23 



hare's-ear or thorow-wax) has no proper place assigned to it 

 ill our j)resent classification. 



This leaTis disposed of by SirWilliamHooker,of course with- 

 out any allusion to its venation, as " perfoliate roundish oval." 

 Its veins are, nevertheless, distributed in a manner so remark- 

 able, as to characterise this leaf from all the other Umbelliferte. 

 A cursory examination only would leave the impression that 

 it was a ribbed leaf; but, on closer inspection, it will be 

 seen that, although the costse have one common origin, and 

 proceed in curves toivards the apex, yet that they never reach 

 it, but join back to back, forming curves like the venae 

 arcuatfe in a netted leaf, and these, again, are joined by a few 

 straggling veins which pass to the margin. 



This leaf, therefore, is not a ribbed leaf, because none of 

 its costse pass to the apex. It is not a netted leaf, becavise it 

 has no primary veins ; but it partakes j)artially of the twofold 

 character of both. Hence I would suggest that its proper 

 position should be called Costato-reticidatum. 



It may be presumed that the addition of a marginal vein in the 

 leaves of the Umbelliferous class is for the purpose of givingsoli- 

 dityand strength to the leaf. I have seen the integrity of leaves 

 destroyed by caterpillars, parasites animal and vegetable, and 

 burns from the concentration of the siui's rays by drops of rain, 

 but I have never yet seen a leaf torn by the wind. This 

 power of resistance is to be attributed partly to the flexibility 

 and elasticity of the boughs and branches, but also to that 

 due adjustment of the fibro-vascular tissue to the parenchyma, 

 the skeleton to the green part of the leaf, whereby this latter 

 becomes ex^ianded in space and supported. Now, the leaves 

 of this order are, many of them, exceedingly thin. Every 

 one at all conversant with the subject wiU know that if such 

 leaves are not submitted to pressure almost as soon as 

 gathered, they curl up and are troublesome to be laid out on 

 paper. Take, for example, the leaves of Conium, ^thusa 

 cynapium, Sison amomum, and a host of others, when, on the 

 contrary, the parenchyma is thicker and stronger, the neces- 

 sity for the vein no longer exists, as in Heracleum, Angelica, 

 and others, while the leaf of Apium graveolens (celery) is so 

 thin that a small type may be read through it when held up 

 to the light. 



The number and course of the veins is, no doubt, very 

 nicely adjusted to the requirements of the leaf, amongst 

 which a state of extreme tenuity would appear to demand a 

 peculiar provision. The netted cordage which envelojoes a 

 balloon contributes, doubtless, in no small degree, to its safe 

 ascent, and its return to the earth without bursting ; while 



