1916-17.] BOTANICAL SOCIETY OF EDINI5URGH 221 



Observations on Rhododendron Seedlings. 

 By Professor Bayley Balfour, F.R.S. 



(Read 12th April 1917.) 



But little information is to be found in botanical books 

 about the seedlings of Rhododendrons. Lord Avebury in 

 his book On Seedlings mentions one species only — Rh. 

 arboreiim. We have at present in the Royal Botanic 

 Garden an assemblao;e of Rhododendron seedlings more 

 varied perhaps than is to be found elsewhere, and upon 

 this what I am to say is based. Whilst the earliest stages 

 of extraseminal development are uniform in the genus, the 

 features of the epicotyl through its juvenile stages show 

 divergences, which we may in time be able to correlate 

 with both phyletic and cecologic factors. In this record of 

 observations I have specially in view to point out characters 

 of transition that appear in the seedlings of species which, 

 as adults, possess an underleaf-indumentum conveniently 

 termed tomentose in the loose terminology of systematic 

 description. 



My attention was first focussed upon the phenomenon 

 I am about to mention by finding that plantlets raised from 

 seed — of the correct naming of which there was no room 

 for doubt — did not show, even in a fifth year of growth in 

 some cases, the technical character of leaf-indumentum which 

 belonged to the species at maturity. That the assumption 

 of adult form by a plantlet may be long delayed is now a 

 commonplace of botanical teaching, to be illustrated by 

 examples from the most diverse families of plants, and 

 reaching even the stage of a permanent juvenility, but I 

 had no knowledge of its occurrence amongst Rhodo- 

 dendrons, nor indeed amongst Ericaceae. 



In the seedlings to which I am referring the foliage- 

 leaves of the early years of growth — which in the matter 

 of shape may be rightly described as miniature of the adult 

 — have the undersurface coloured an intense, often very 

 dark, red due to the presence of anthocyanin pigment, which 

 develops not only in the epidermis, but also in the meso- 

 phyll. Commonl}^ too the surface is sprinkled with capitate 



