l6 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
of these, such as ah' c, a h' c' , a' h' c, a' b c, and so on. The best- 
marked variant from the type abc would be a' b' c', and even such 
a form as a b' c' might be allowed varietal rank were it not for the 
existence of the forms ab' c and abc'. To this must be added the fact 
that a, b, c, a', b', and c' are not constant quantities, but exist in inter- 
mediate degrees which connect a and a', and so on. Thus, glaucescence 
may vary by imperceptible degrees into green, and an ovate leaf 
into a lanceolate or linear leaf. So that in diagnosis we have to deal not 
only with the number of characters in which a form may agree with 
or approach a well-marked variety, but with the degree in which 
each of these characters is present. To conclude, the study of a large 
growing series of forms of the variable species of Sedum as found in 
cultivation puts one out of conceit with the application of varietal 
names to most of them. 
But it may be pointed out that, owing to the absence of inter- 
mediates in a given area, such forms may assume a very definite local 
importance, which may fully justify their being dealt with in local 
floras, though on a wider view their distinctness may disappear. It 
may be added that the study of a large series of Sedums derived from 
garden sources has this bearing on the botanical as opposed to the 
horticultural side of the question : that as Sedums are almost invari- 
ably propagated by division, and as they do not tend in most cases 
to seed themselves in gardens, the numerous garden forms un- 
doubtedly mostly represent wild forms, and give a true conspectus 
of the natural range of variation of the different species. 
VI. Cultivation and Propagation. 
Most Sedums are of the easiest cultivation, and given perfect 
drainage and a light soil no difficulty will be experienced. Many — 
though not all — are especially at home on an old wall,' where they 
will withstand any degree of drought. The vitaHty as against want 
of water of many Sedums is indeed remarkable, and few plants are 
better fitted to endure the adverse conditions of soil and moisture 
which are found, say, on a wall-top. But it would be a mistake to 
imagine that such conditions are necessary or favourable to their 
growth. The majority flourish best under ordinary garden treatment ; 
some, such as the Telephiums, prefer a rich moist soil ; and one or 
two, such as the European S. villosum and the North American 
S. pulchellum, though possessing a succulence as great as many of 
the most xerophilous species, actually require in many gardens marshy 
conditions to secure their continuance. 
The majority of the Sedums found in cultivation are quite hardy 
in our chmate, but a considerable minority cannot be so classed. 
Thus, the Mexican Sedums come from a tolerably warm climate, 
and as a whole are best suited to a cool house. Their hardiness in 
the British climate has not as yet been fully tested save in a few 
