Tricot yl\ and flic Avnuiijciiioit of Leaves. Z77 



the cotyledons and especially a splitting equally deep on 

 the two sides may involve an alteration in the disposition 

 of the leaves. This, of course, is by no means a neces- 

 sary consequence, but the present case indicates that the 

 internal cause is not necessarily limited in its operation 

 to the cotyledons. 



Terminal leaves have hitherto been regarded by tera- 

 tologists as very rare occurrences, but my tricotylous 

 races of Antirrhlnnin uiajiis have afforded me the oppor- 

 tunity of observing them repeatedly and in hundreds of 

 specimens (Fig. 81). 



A well-known instance is the great terminal leaf of 

 Gcsiicra Gcroltiana described by Morren and reproduced 

 by Masters/ This specimen bears only one normal 

 pair of leaves, and above these an erect leaf of double 

 the normal size. In the figure we can see the node at which 

 this is inserted; and the simplest explanation of this 

 remarkable phenomenon is that, for some reason or other, 

 the growth of the second leaf of the pair, as well as that 

 of the terminal bud was impeded in early youth. Ber- 

 noulli mentions a similar apparently terminal leaf of 

 Coffca arabica, and was able in this case to confirm the 

 correctness of this supposition by microscopical obser- 

 vation.^ He also describes a shoot of Fuchsia iiiacro- 

 stcmina which bore a funnel-shaped leaf at the top. 



The races of the Snap-dragon, which we have already 

 mentioned bear every variety of these structures. These 

 may consist of single or of double leaves, or of leaves 

 grown together in the shape of a funnel. All inter- 

 mediate stages between these and the normal plants oc- 



'Ch. Morren. Bull Acad. BcJo., Vol. XVTT. Part IT. p. 2>^7\ 

 M. T. Masters, Vegetable Teratology, p. 88, Fig. 40. 



^ G. Bernoulli, Ueher scheinhar terminale Blatter, Botan. Zei- 

 tnng, 1869, p. 19. 



