562 71. AMENTIFERA. 
very clear knowledge of these difficult plants in their living reality 
and wild condition. At any rate, they have more usually re-said 
than added to previous knowledge. And I assume that they have 
taken their descriptions mainly from Smith or Borrer, more or less 
assisted by dried specimens; that is, by a limited supply of 
fragments in the herbarium. 
Unisexual trees and shrubs, numerous in species and very 
numerous in varieties, whose flowers precede the leaves, and 
which perhaps often hybridize, and certainly sport much into 
subordinate variations of form and pubescence, would require to 
be illustrated by an extensive series of good specimens in the 
herbarium, in order to yield a sufficiency of materials for their 
technical arrangement and description in books. The difficulty 
of this is increased by their great liability to the attacks of insects, 
if left undisturbed in the herbarium for any considerable time. 
Few botanists are in a position to devote sufficient space to a living 
collection. Take our own insular Willows at 80 to 100 named 
segregates. Double that number for the sexes. Allow the 
inadequate average of half-a-dozen examples to each sex of each 
segregate, to illustrate its sub-variations in form or pubescence ; 
and then a thousand living trees or bushes would not be found 
unnecessarily numerous, as a fairly good living collection. To 
examine them in their native localities (and in Osier grounds) from 
the South of England to the Arctic zones of the Highland hills, at 
several different times in the year, and for several years in 
succession, returning even to the very same individual bushes at 
different seasons, is obviously a requisite which can be achieved 
only in very limited degree by any one botanist. 
The first of the four describing botanists above mentioned has 
very candidly put on record his own kind of preparedness or 
qualification for the task of describing Willows. But for the 
difficulties specially appertaining to this genus, it might reasonably 
have been expected that his Mlora Scotica would have been a 
descriptive account of plants actually found in Scotland, and made 
on living examples or herbarium specimens really of Scottish 
growth. And yet he introduces his account of the Willows of 
Scotland by the frank admission conveyed in these words : —“ The 
following specific characters of this most intricate genus are taken 
in every instance, where not otherwise mentioned, from specimens 
that are the best authority for the H. Bot. species; that is, from 
individuals gathered in the late Mr. Crowe’s garden near Norwich, 
in company with Mr. Crowe himself, or with Sir James Smith. If 
my characters differ in some measure from those published by Smith, 
it will show how variable these plants are, and how careful we 
ought to be in not multiplying the species unnecessarily.” 
Sir James Smith himself had seen little of British botany in the 
wilds. For willows he too trusted much to Mr. Crowe’s garden, 
