BOTAXICAL SUBJECTS. 149 



the pairs of leaflets wliicli shoald not be there, as there is no room 

 for them ; (6) are the secondary pairs of leaflets, which should not 

 be there either, as they belong to a decompound leaf and not to a 

 bipinnate one ; (Jj, h) are there by reversion, in this particular 

 abnormal pinna, which I copied from nature. 



9. One of the most interesting examples of the abortion of 

 leaflets into stipels I have come across is in the drawing of Vicia 

 hii'suta, given in Syme's " Brit. Bot.," Fig. 36. The two lower leaves 



Fig. 36. Lower leaves of Vicia hirsuta (Syme, " Brit. Bot.," pi. 382) : — 

 (a) leaf with some of the pinnse atrophied, (6) leaf with all the pinnae 

 atrophied and converted into stipels, or teeth. 



have their leaflets either totally or partially converted into stipels 

 or teeth. This and the leaf of Hardenhergia Coinxdoniana show 

 without doubt how the stipels of leaves and teeth should be 

 interpreted. 



10. A palmate or digitate leaf is nothing but a pinnate leaf, 

 shortened. The palmate leaf is only a partial fasciation of the digi- 

 tate variety. If digitate or palmate leaves were upright, they 

 would be verticillate divisions of the petiole or stem-branch, as in 

 Rodgersia 'podophijUa. The leaves of the latter are erect, because 

 the stem proper is recumbent, as a rhizome. If the stem were, on 

 the contrary, erect, and the leaves horizontal, then the leaflets 

 would have arranged themselves, as in the horse-chesnut, with those 

 nearest the petiole smaller. Why they are smaller it is not easy to 

 say, but we find that the leaflets nearest the petiole are often subject 

 to starvation, and consequent depauperization and atrophy, as in 

 the stipels of Wistaria. 



11. Similarly, Diphylleia cymosa has a palmately lobed leaf, when 

 horizontal, but when erect it becomes peltate, and divided into two 

 equal portions, as in the diagram, Fig. 37. 



Begonia carolinicefolia has leaves similar to those of Rodgersia, 

 but with eight verticillate leaflets, and a potential bud in their 



