Occurrcnrx of Foliarjc-lcavcs in Euscus androgynus. 137 



of the fibro-vascular buudles are d.sposeJ as iu ordinary 

 leaves; t.e., the phloem portion of the bundle is placed 

 towards the lower surface, and the xylem portion towards 

 the upper surface. In the cladode of that plant, on the 

 other hand, the position of these elements is reversed ; the 

 phloem being towards the morphological upper surface, tlie 

 xylem towards the morphological lower surface (Plate X. 

 fig. 1). In the cladodes of B. racem.osus and Myrsiphyllum 

 asparagoides, I have found the same arrangement. In the 

 barren cladodes of R. Hypoglossum, the same is also usually 

 to be seen ; but sometimes there seems a tendency in the 

 middle bundle to be multiple, witii the elements variously 

 directed, — in evident connection with the possihilty of the 

 emergence of an inflorescence in the middle line. In the 

 barren cladodes of R. aculeatus, the position of the fibro- 

 vascular elements does not seem to be very constant : 

 usually the phloem is directed towards the morphological 

 upper surface, as in the other cases ; but sometimes — 

 especially in the smaller veins — the phloem and xylem 

 are placed obliquely to the surfaces of the cladode, or may 

 even have an altogether reversed direction. 



The direction of the phloem elements of the fibro- 

 vascular bundles towards the morphological upper surface, 

 to be seen in these cladodes, and most clearly in those 

 forms where the leaf-like specialisation of the cladode is 

 greatest, as in R. racemosus^ R. androgynus, and llyrsi- 

 phyllum asparagoides, is very interesting, and is, it seems 

 to me, of great importance from a morphological point of 

 view,* especially in connection with the vexed questions of 

 the constitution of the squama frudifera of Conifers and 

 of the "needle" of Sciadopitys, — questions on which I 

 would take this opportunity to make some remarks. 



A. As to the squama friictifera, Schleiden was the first 

 to question the accuracy of Robert Brown's idea that it 



* At first sight, oue is tempted to inquire whether the position of the 

 fibro-vascular elements may not have some relation to the development of the 

 stomata on one or other surface. That, however, there is no such relation, and 

 that the position of these elements has a morpholocjical rather than a physio- 

 logical significance, is proved by the fact that in the twisted leaves of Alstrcc- 

 mcria, Bomarea, and Luziiriaga, the position of these elements is the same as 

 in ordinary leaves (viz., the xylem to the mor[)hological upper, the phloem to 

 the morphological lower surface) ; while in the cladodes under consideration 

 these elements have the reverse position, whether the cladodes are twisted, as 

 ^in R. androgynus, or not, as in Myrsiphyllum asparagoides. 



