Miscellaned'us, 71 



firms the views of some botanists, as I have learned from Professor 

 Asa Gray, that it is by metamorphosis of the petiolar and stipular parts, 

 rather than by modifications of the leaf-blade, that petals are formed. 



From these facts we gather the certainty of a trilobate type of 

 leaf and see the aduation of the edges ; and only the dorsal adhesion 

 to the petiole, which I have shown so probable as almost to amount 

 to a certainty, is left to be established by actual fact. 



This ternate division of the leaf is a marked character in Eanun- 

 culaceae ; and with this exposition of a ternate type in Magnoliacese, 

 its claim to a place in the Eanal alliance, strong as it always has 

 been acknowledged to be, is still more strengthened. 



It is impossible to suppose that a genus so closely allied as Lirio- 

 dendron should be founded on a different type from Magnolia. We 

 shall see that only very slight causes, which we can well understand, 

 have made some of the chief foliar distinctions ; and the few which 

 we cannot prove from actual facts can be made almost certainties 

 from parallel observations. The identity of type will in this way be 

 manifest. 



First, as to the premorse or cut-off appearance of the end of the 

 leaf-blade. This all results from the stipular portions being adnate 

 with the stem-axis, instead of being wholly on the petiole as in Mag- 

 nolia. In the latter the stipules are carried along as the petiole 

 advances, the leaf-blade cannot grow beyond, and so in vernation has 

 to lie flat up against them. In Liriodendron, the stipules being fast 

 to the main stem, the petiole carries the leaf-blade beyond them, over 

 which it is bent until its apex is brought down in contact with the 

 straight line formed by the union of stipule and stem. Hei-e it is 

 pressed as into a mould by the elongating petiole, and the form of 

 the leaf which we see is the necessary result. These processes in 

 Magnolia and Liriodendron can readily be seen on an examination of 

 the buds at any time during the growing-season ; and to those who 

 have no specimens the figure of the latter in Gray's 'Genera' wiU easily 

 give the idea. It may be here noted that those who look only to 

 Mr. Darwin's principle of natural selection to account for the laws 

 of form, might be troubled by such cases as these. It is scarcely 

 conceivable that a square-edged leaf-blade, as we find it in Lirioden- 

 dron, is of any special benefit to the species ; yet if this form is the 

 consequence of some other act which is a benefit, the selection 

 principle may still hold. 



If the ternate type of leaf is probable in Liriodendron, as in Mag- 

 nolia, the lower portion of the petiole, and lateral or stipular por- 

 tions, must have adnated with the stem prior to the full development 

 of the leaf. This view necessitates the idea that the leaf does not 

 always originate at the node from which it seems to spring. I do 

 not believe it does ; but I am well aware that in this I have opposed 

 to me the weight of our best botanical authorities, fi'om whom 1 

 would not yet dare to differ until I shall have the weight of more 

 facts. I would only say that in the case of Liriodendron the appear- 

 ances are much in favour of the belief that in an early stage the 

 petiole clasped the stem, and for a considerable length ultimately 



