'1 



p I - _■ 



1- 



^»T -r 1 ; 



TT 



OF CERTAIN MONOCOTYLEDONS. 



471 



Our present interpretation of the solid apices of MonocotyleJonous leaves, 

 as being vestigial petioles, does not appear to have' been proposed by any 

 previous writer, but I have lately learned thai HalHer *, in a discussion of 

 the nature of the parts of the Angiospcrmic flower^ has put forward a view 

 wiiich is very suggestive iu this connection. He draws attention to the fact 

 that certain Dicotyledonous sepals terminate in a point wliioli he 



calls 



s a 



•'^ cornet^' or ^^aiirailli. 







He treats tlie case of llymenogyne glabra, Haw. 

 Jetail, and points out that^ on comparing the outer 

 sepals of this plant with tlie foliage-leaves — which towards the base are 

 gradually reduced to long membranous i^heaths — one recognises at once that 

 the winged region of these sepals corresponds to a leaf-sheath and the point 

 to an aborted petiole. He considers that the same explanation applies to 

 such structures as the awned glumes of the Graminese. Hallier draws the 

 general conclusion that th^3 sepal of the Angiosperm is the sheath of a bract, 

 which in some rare cases has preserved the remains of the petiole in the 

 form of a *^ cornet." To tlie cases cited by Hallier, we may add that of 

 Clematis^ certain garden forms of which show a conspicuous " aio-uilla " 

 which is. howevf^r. small in comnarison with the sftunl n>? n wholn 



■'1. 



(Si?- 11) 



of the genera mentioned by Hallier, and I have found that not only in the 

 external fornij but also in the anatomical structure, there is a close resem- 

 blance between these floral leaves and the foliage-leave's of such plants as 



Klegia and DisticMa (cf. 



with figs. 5 A and B, and figs. G A-l)). 



In both cases there is a more or less complete ring of bundles in the apical 



point. 



If 



i/?' 



credence can scarcely, in consistency, be refused to the interpretation of the 

 foliage-leaves of Eleqia and Disticlda i)roposed in the present paper. 



2. Spatlie-leaves of llie Type of Ludovia crenifolia, Driale. 



m 



Cerlain spathe-lcavcs associated with the inflorescence in the PalmSj 

 Aroids, and (Jyclanthacoce, appear to have a solid cylindrical apex, com- 

 parable to that of the foliage and floral leaves considered in the preceding 

 section of this pa[)er. I do not propor>e to deal with these spathes in detail 

 now, as I think it vvid l)e more satisfactory to treat them,later^ in connection 

 with the leaf-morphology of the Families to wliich they belong ; but one 

 case from the Cyclanthacete may be described as an example. 



The inflorescences of the Cyclanthacea} are enclosed in 2-G boat-shaped 

 spathes* I have been able to examine three such spatheJoaves from an 

 inflorescence oi. Ludovia crenifoUa^ Drude; they differed in detail, but a<Treed 

 in p'ossessing ;i solid cylindrical apex. Fig. 12 a shows the dorsivcntral 

 structure a short way below the tip ; still lower the sheath opens out, and 



* riallier, 11. (1912), pp. 191-2. 



2l2 



