202 
_ cistus, Rehb. (Rhododendron Chamaecistus, L.), now known to be 
confined to the Eastern Alps (and Southern Translyvania ?), to 
which it bears a very close external resemblance. This erroneous 
determination was also recorded by H. E. M. James in the list 
_ of plants appended to his account of a journey in Manchuria 
entitled “‘The Long White Mountain,” p. 458 (1888). James 
collected the plant between Mukden and Kirin. 
Therorhodion camtschaticum occurs on both sides of the 
Behring Straits, 7. Redowskianum in Eastern Manchuria (see 
also p. 205), and T. glandulosum in North West Alaska. The 
genus differs from Rhododendron proper by the flowers being 
borne on the young leafy shoots, and not in special buds as in 
the case of all true Rhododendrons, and in the unilaterally split 
corolla-tube. In the case of Therorhodion Redowskianum 
especially, and to a much less extent in that of 7’. kamtschaticum, 
the style (see Fig. 1) is very early abruptly reflexed from the 
base and projects through the sinus of the split corolla-tube, thus 
entirely removing its stigmatic surface from the stamens and 
effectively preventing self-fertilization. One might reasonably 
suppose that during the course of evolution of this interesting 
little genus the bending of the style, in order to avoid self- 
fertilization, has. been a gradual process associated with the 
visits of insects, and has brought about a corresponding gradual 
splitting of the corolla-tube. 
Below is given a key to the species of Therorhodion with a. 
revised description of the two species represented at Kew. 
Therorhodion, Small in North Amer. Fl. xxix. pt. i. 45 (1914). 
Rhododendron § Therorhodion, Maxim. in Mem. Acad. St. Petérsb. 
ser. Vil. xvi. n. 9, p. 47 (1870). 
Leaves not glandular-ciliate; corolla pube- 
scent outside, the lobes much longer than 
the tube; calyx-lobes veiny; style nearly 
as long as the corolla, not reflexed  ... 1. camtschaticum. 
Leaves glandular-ciliate; corolla glabrous 
outside, the lobes longer than the tube 2. glandulosum. 
Leaves glandular-ciliate; corolla glabrous ° 
outside, the lobes about as long or a 
little shorter than the tube; style much 
shorter than the corolla, abruptly re- 
flexed and protruding through ¢ the sinus 
of the split corolla . Redowskianum. 
1. Therorhodion ‘genic’ Small, 1.c. (1914). 
Rhododendron camischaticum, Pallas, Fl. Ross. i. 48, t. 
(1784); Hook. Fl. Bor. Am. ii. 43 (1834); Maxim. Le. 47 “iste; 
Hutchinson in Bot. Mag. t. 8210 ( 1908). Rhodothamnus kamt- 
schaticus, Lindl. in Paxt. Fl. Gard. i. t. 22 ( 1850). Chamaerho- 
dodendros Berberis At etc., Gmel. Fl. Sibir. iv. 126 (1769). 
Rhododendron Chamaecistus, Linnaane; Mant. 381 (1771), quoad 
syn. Gmel., non pl. penis 
