86 Dr. Wight on the Separation of the Pomegranate 



whether such is always the law of evolution, and taking 

 place in every plant, is, I think, not sufficiently proved. In 

 Tilia especially this law, however, can be seen operating, in 

 the formation of the spiral fibres on the wall of the cells of 

 the pleurenchyma. That the continuous spiral development 

 is the base of all forms of annular reticulated and dotted 

 vessels I think certain, and the various metamorphoses which 

 arise from such base are to be sought for in the peculiar 

 after-growth of the primary structureless membrane upon 

 which the secondary fibrous layers were originally deposited. 

 Very often, as may be seen in Tilia, this membrane becomes 

 entirely absorbed, the coils of the secondary spire brought 

 close together ; and this happening during the development 

 of the fibres, the spiral continuity ceases to exist ; the mole- 

 cules from which the fibres are formed hence pass into a 

 series of more or less broad, flat, and continuous bands ; and 

 vessels formed of such fibres, totally destitute of primary 

 membrane, are to be found in the plant just referred to. In 

 fact, much of the tissue of Tilia represents many stages and 

 states of evolution of the secondary fibrous layers in con- 

 nexion with peculiar after-growth of the primary structure 

 upon which they have been deposited. I have observed com- 

 pound spiral vessels in the petiole of Tilia pubescens. 



4. — On the under surface of the leaf of Adelia nereifolia 

 may be found a very beautiful and peculiar form of scale ; it 

 consists of two circular layers of cellular membrane, the one 

 layer of much smaller diameter than the other, puckered and 

 plaited, and of a saucer-shaped form ; it is fixed by its centre, 

 which apparently is connected with a gland having coloured 

 contents. From this form of scale, through that met with on 

 Eleagnus conferta, I think transitional states may be seen, to 

 the stellate hairs of many of the Euphorbiacece and Malvacece ; 

 in fact, upon the peculiar adhesions taking place between the 

 cells depends the appearance of the stellate hair or the scale of 

 Adelia and Eleagnus. The occurrence both of stellate hairs 

 and this form of scale in Euphorbiaceae, shows the structural 

 differences between the two not to be great in their origin. 

 [ To be continued.] 



X. — On the Separation of the Pomegranate as a distinct 

 Natural Order from Myrtaceae. By Robert Wight, 

 M.D., F.L.S., &c. * 



The most eminent botanists of the present day being divided 

 in opinion as to the propriety or otherwise of separating the 



* From the Madras Journal of Literature and Science, No. xxix. p. 254. 



