1915-16.] BOTANICAL SOCIETY OF EDIXBURGH 99 



12,000 ft. Shrub of 15-25 ft. Flowers pale yellow. 

 Forrest No. 4160. Aug. 1906. 



Yunnan. Rhododendron forest. Eastern flank of the Tali 

 Range. Lat. 25° 40' N. Alt. 12,000 ft. Tree of 20-30 ft. 

 Flowers pale yellow, fragrant. Forrest No. 6778. Aug. 

 1910. 



Yunnan. Rhododendron forests. Western flank of the 

 Tali Range. Lat. 25° 40' N. A shrub of 15-25 ft. Alt. 

 12,000 ft. Flowers pure canary yellow. Forrest No. 

 11,575. June 1913. 



And then there are the following specimens, which are 

 certainly the same as Delavay's No. 2214 and are therefore 

 Rh. lacteum, var. meter ophy Hum, Franch. : — 



Yunnan. Above the pine belt on the Sung Kwei — Lang 

 Kung divide. Lat. 26° N. Alt. 13,000-14,000 ft. Forrest 

 No. 501. Dec. 1904. 



Yunnan. Open situations in pine forests on the descent 

 from the Sung Kwei pass to the Sung Kwei valley. Lat. 

 26° 15' N. Alt. 10,000-11,000 ft. Tree of 20-30 ft. 

 Flowers white fleshy with a blotch of rich crimson at base 

 of corolla. Forrest No. 2159. April 1906. 



Careful examination of this material shows to me that 

 the differences separating Rh. lacteum, var. 7nacr ophy Hum, 

 Franch. from Rh. lacteum, Franch. are more than varietal 

 and that we have before us here two quite distinct species. 



Apart from many minor differences there are two 

 characters by which RIl. lacteum, Franch. and Rlc. lacteum, 

 var. macrophyllum, Franch. can be readily distinguished 

 one from the other. These are : 



a. The indumentum of the under surface of the leaf : — 



Genuine student as he was of Rhododendrons, Franchet 

 came to recognise the importance of the indumentum as a 

 diagnostic mark within the genus, and as bearing upon the 

 immediate subject of discussion here I quote from one of 

 the pregnant notes which he usually attached to his 

 diagnoses of species after the earlier ones. Writing of 

 Rh. sanguineum, Franch. he says : — " La couche crustacee 

 qu'on observe a la face inferieure des feuilles de quelques 

 Rhododendron n'est souvent que la strate inferieure d'un 

 veritable tomentum ; mais dans le Rh. sanguineum ainsi 

 que dans le Rh. lacteum. et quelques autres, I'indument 



