ioi3 
Multiseriate Ray of the Dicotyledons , 
2. Originating from the breaking up of compound rays, the multiseriate 
ray has spread throughout the wood in the higher dicotyledonous Angio- 
sperms. 
3. Reversion to the ancestral compound type of ray may be observed 
in the seedling, root, &c., of dicotyledonous plants which are characterized 
by the multiseriate type. 
4. The multiseriate ray represents the most recent development in ray 
structure among the Dicotyledons. 
The writer has carried on this investigation in the Phanerogamic 
Laboratories of Harvard University as an 1851 Exhibition Science Re¬ 
search Scholar from the University of Toronto. He is greatly indebted to 
Professor E. C. Jeffrey for direction and material, and to Mr. I. W. Bailey 
for innumerable kindnesses. 
EXPLANATION OF PLATES LXXVII AND LXXVIII. 
Illustrating Mr. Thompson’s paper on the Origin of the Multiseriate Ray. 
PLATE LXXVII. 
Fig. 1. Rhododendron pundatum. Transverse section above the node, showing broad ray 
breaking up into several multiseriate rays, x 12. 
Fig. 2. The same. Tangential section, showing leaf-trace and group of rays above it. x 25. 
Fig. 3. Ledum greenlandicum . Transverse section above node, showing the splitting up of 
broad ray and horizontal spreading of the multiseriate rays, x 12. 
Fig. 4. The same. Tangential section, showing the multiseriate rays above the leaf-trace, 
x 25. 
Fig. 5. Kalmia angustifolia. Transverse section through the nodal region, showing unbroken 
broad ray, two groups of multiseriate rays resulting from the breaking up of broad rays, and two 
multiseriate rays extending up from a lower node, x 12. 
Fig. 6. The same. Tangential section, showing the group of multiseriate rays above the leaf- 
trace. x 25. 
Fig. 7. Vaccinium corymbosum. Transverse section, showing breaking up of a compound ray 
and independently arising multiseriate ones, x 45. 
Fig. 8. The same. Tangential section, x 45. 
Fig. 9. Clethra alnifolia. Transverse section, showing uniform distribution of multiseriate rays, 
x 50. 
Fig. 10. The same. Tangential section, showing the same uniform distribution, and also 
absence of aggregation above the leaf-trace, x 50. 
Fig. 11. Grevillea robusta. Transverse section, showing splitting of broad ray. x 60. 
Fig. 12. Hakea sp. Transverse section, showing splitting of broad ray as in Grevillea robusta 
(Fig. 11). x 60. 
PLATE LXXVIII. 
Fig. 13. Casuarina glauca. Tangential section close to the pith, to show the large compound 
ray. x 45. 
Fig. 14. The same. Tangential section some distance from the pith, to show the network of 
fibres which breaks up the compound ray. x 45. 
