MR. F. N. WILLIAMS ON THE GENUS SILENE. 15 
occasionally they are contorted. There is also an interesting 
note in J. Gay’s handwriting on specimens of Arenaria pungens 
in reference to this same character :—“ Petalorum eestivatio 
nunc imbricata, nunc sinistrorsum contorta.” I consulted the 
late Sereno Watson (who has studied the North American 
species of Silene) as to his views on the importance of these 
primary characters. In a letter received from him only a few 
weeks before his lamented death, he ‘says :—‘‘I have never 
considered the characters that you mention of any special 
importance, and have paid them no attention. If S. Douglasii 
and S. nivea are to be separated from our other species on the 
imbrication of the petals, it is evident that the division is not a 
natural one.” Again, “estivatio alternatim contorta’”’ is some- 
what obscure, but Mr. Watson points out that it appears to be 
illustrated in Eichler’s ‘ Bliithendiagramme,’ on p. 106, fig. 414 ; 
and is what is called ‘“‘antidromy” or ‘ heterodromy,” the 
petals in the flowers of the axis overlapping in one direction, 
and those of the branches in the opposite. Now the species of 
Silene are difficult to discriminate in living specimens, especially 
before the ripening of the capsules, and still more so in the case 
of herbarium specimens; and were the mode of imbrication of 
the petals, if such variation is to be depended upon, to be 
insisted on as a primary character, it would of necessity impair, 
if not stultify, the value of the Yesult obtained from an 
attempted examination of the greater part of the material 
afforded by collectors and distributors. I propose, therefore, by 
slightly modifying Rohrbach’s arrangement, to base the primary 
subdivisions of the genus on the structure of the calyx ; and to 
exclude from his subgenus Behen those few species in which the 
two characters of a calyx with anastomosing veins and inflated 
at the time of flowering are not associated, viz., S. pygmea, 
S. turgida, and S. Douglasii. I propose also to follow Engler 
and Prantl* in considering each division of Silene proper as a 
Subgenus, thus making three subgenera instead of two. I 
would further suggest Gastrosilene as a substitute for Behen, 
which is somewhat of a misnomer. Cucubulus Behen, Linn., and 
Behen vulgaris, Moench, are certainly superseded names for 
Silene inflata, the best known species of the subgenus, but 
Silene Behen, Linn., is a good species, and belongs to another 
Subgenus, so that the name as taken up by Rohrbach is mis- 
leading. Gastrosilene is pseudhomonymic also with Gastrolychnis, 
* Die Natiirlichen Pflanzenfamilien, Theil iii (1889), p. 70. 
