p, T-*- 



6f certain monocotylkdons. 



473 



of the Musacese, but it occurs also in other Families [e.g., species of Calla, 

 Antkurium, DiefenhacJiia, and Philodendron of the Aracee35 and Smilax 

 aspera^ L., of the Liliacea}). 



In tlic case of Smilax^ I have already suo-gested * ihat the thickened tip 

 of the limb may represent the last relic of the unexpanded petiolar apex 

 that is to say, the expansion that formed the pseudo- lamina, though it 

 involved the distal region of the petiole, did not extend* to the extreme tip. 

 In this connection it is interesting to notice that there is some evidence 

 tliat Smilax aspera Is one of the oldest members of the genus. The points 

 in favour of this view are that it belon^-s to tlie lareesfc Section — ]^usmila^\ 

 DC-; that it is one of tlie four most widely-ra»iging members of this Section, 

 which are also the four most widely-distributed forms among the 186 species 

 making up the genus as a wliole t ; and that it occurs in a large number 



Fig. 14. 



LEAF TIP OF MUSA 



Fig. 14, — 3fusa Basjooy Sieb. Series of transverse sections through tip of one foliage- 



]eaf ( x23). 14 a, section of limb a little below solid apex; the limb 13 rolled in the 

 bud in a counter-clockwise direction^ but as this series is taken upwards from below^ 

 the direction appears reversed; f.?^^ = tracheal mass ; /rro.^lacuna; 14 b, section at 

 transition to solid apex; 14c & D show fusion of tracheal masses to an arc, ^.«, 

 In 14 E the vascnlar system is reduced to a small group of elements, which seem to 

 be chiefly tracheids. 



1 



ofvarieties* S. aspera is thus one of the species of Smilax in which it 

 wouldj a prioriy be least surprising to find some trace of the petiolar origin 

 of the pseudo-lamina. 



The case of the Musacese is particularlj striking. The young leaves aro 

 rolled in the bud, and aro usually characterised by an ephemeral elongated 

 apex, approximately cylindrical in form, which shrivels at an early stage. 

 Material of very young leaves of Musa can, naturally, only be obtained in 

 small quantities in this country^ but I have been able to examine one young 



« 



Arber, A. (1920^)^ p. 440 ; the S, mauretanica of this paper is better regarded as a 



variety of 8, aspera. 

 t Caadolle, A. de (1878), p, 29/ 



I- . 



