1486 ARBORETUM AND FRUTICETUM. PART III. 
dom happens before the beginning of summer. On the other hand, very many 
sorts, in intermediate localities, are intermediate also in their time of flowering. 
Hence, the same kind, when it inhabits three different regions, cannot be 
compared together in the same stage of growth in a living state ; and, conse- 
quently, three species may, in this way, be made out of one. Dr. Host farther 
observes, that a great impediment to the determining of what are really species, 
arises from the sexes of a species often inhabiting localities very distant from 
each other, and sometimes even different regions; and the beautiful figures which 
illustrate this author’s work, on the supposition that they are faithful portraits, 
clearly show that the male and female differ very considerably in their foliage 
and wood, independently altogether of their catkins. 
The great master in the genus Salix may be considered Professor Koch, 
who has done more to advance a knowledge of this genus in his 12mo pam- 
phlet of 69 pages, De Salicibus Europeis Commentatio, published in 1828, 
than the most voluminous of ancient or modern authors. The preface to this 
pamphlet is so full of instruction as to the mode of studying this family of 
plants, that we are confident that our readers will feel obliged to us for pre- 
senting to them the following 
Abstract of Koch's Preface to his Commentary ou the Genus Salix. The author, 
after noticing the difficulties to be encountered in this genus, and referring to 
what has been done by Linnzeus, Wahlenberg, Willdenow, Smith, and others, 
notices the 119 species which had been sent to him by Schleicher, as found 
by that botanist in Switzerland, and thus, as we have before observed (p. 1456.), 
making the total number of species of Salix 254. Of Schleicher’s species, he 
says that he could not find one that truly deserved the name.. They are, he 
adds, mere variations of species long since known; and, for the most part, dif- 
ferent forms of one changeable species, viz., his own S. phylicifolia. All 
Schleicher’s kinds are enumerated as species in Steudel’s Nomenclator ; but 
Koch treats them as spurious, he recognising not more than 50 truly distinct 
European species. 
The manner in which Koch obtained his knowledge of the genus Salix is 
thus given:—“ For a number of years, I observed the willows growing wild 
in the Palatinate ; also those I met with during my travels; and those which I 
have found, during the space of four years, in the neighbourhood of Erlangen. 
All the species, or singular forms, which I found growing wild were trans- 
ferred to the garden; and to these were added kinds sent by my friends 
Mertens and Zeiher, an addition of no small importance. From the former I 
received genuine English willows ina living state. The whole collection was after- 
wards transferred to the Botanic Garden at Erlangen, where, neither care nor 
expense being spared, it has since been much increased. From M. Otto 
director of the Botanic Garden at Berlin, I also received a number of kinds. 
Of dried specimens | have received the whole collection of M. Seringe, from 
that author himself; and the greater number of the Swedish, French, and 
English willows, gathered in their native habitats, from Mertens ; forming in 
the whole a greater number of species of this genus than was ever before 
available by one individual. 
“ Every genus of plants has certain peculiar features, with which constant 
observation and repeated examination alone can familiarise us; but there is 
no genus in which it is so necessary as in that of Salix, to investigate, not only 
its peculiar characters, but also the growth of the plants, both in a wild anda 
cultivated state. He who endeavours to characterise a species, either from a 
dried specimen or from a cultivated plant, is always liable to be deceived in 
its characters. Hence, amongst all the writers on willows from the time of 
Linnzeus, Wahlenberg alone has clearly described them. He travelled through 
Lapland, Switzerland, the Carpathian Mountains, and Sweden; examining 
the kinds of this genus in their native places of growth ; and, following in his 
footsteps, came Seringe, also a most diligent investigator. Taking these 
authors for my guide, although, in some instances, I have been compelled to 
differ from them, I here offer a synopsis of the European species of willow. 
“ In arranging this genus, and distributing its species, if we put near together 
