PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
211 
acters of both the parents in equal measure. But not only- 
do they not do so, hut as they are—though hybrids— quite 
capable of reproducing themselves, and being in their turn 
hybridised, we find secondary hybrids— i.e., forms in which 
the characters of three species are combined—not unfre- 
quently arising, and thus adding to the perplexities of the 
student. 
That | you may more clearly understand what is 
meant, let me briefly describe the structure and mode of 
fertilization of the flowers of a willow. The flowers, as 
you probably know, are massed together in spike-like 
masses called catkins, and the plants are what is termed 
“dioecious;” that is to say, only one kind of flower as 
regards the sex is found on an individual bush—one bush 
having pollen-producing flowers oaly, and another seed- 
producingflowers only. Rarely, and indeed as a monstrosity 
only, does the same catkin have both kinds of flowers. As 
for the fertilization, this is chiefly effected by the agency 
of insects. The flowers are odorous, and produce a greater 
or less quantity of nectar, which attracts insects of various 
species. These visit either kind of plant indifferently, and 
as the pollen readily adheres to them, they unconsciously 
convey it to the pistils of the seed-producing plants, and 
effect fertilization. 
In the vast majority of cases the fertilization thus 
brought about is by the pollen of the same species as that 
of the fertilized plant, but it can readily be seen that in 
some cases the fertilizing pollen may be that of another 
species, and thus a hybrid be produced. 
Why hybrids are not more frequent than they are may be 
due to several causes. Though many species of willowsflower 
about the same time, yet there is often a little difference 
in the exact time, and thus the right pollen is brought to 
the right plant. Again, it is probable, though about this 
we are uncertain, that the pollen of one species does not so 
readily fertilize a different species as it does its own species, 
and hence the number of individuals of hybrids is limited. 
I spoke a little while ago of hybrids in which the charac¬ 
ters of three species were combined. To make my mean¬ 
ing clearer, I will express this in another way. If we take 
the letters A, B, C, &c., as standing for good and distinct 
species, the progeny of a cross between A and B may be 
expressed as A-B, and similarly between A and C as A-C. 
New, keeping in mind that these, like their parents, are 
usually perfectly fertile, A-B or A-C may in their turn be 
crossed by D, the resulting progeny being A-B-D, or 
A-C-D as the case may be, which would be a form in 
which the characters of three species are combined. But 
instead of D entering into the composition of this second¬ 
ary hybrid it may happen that it is one of the parent 
species, with the result that we get this formula, A-B-B or 
A-C-C. Continue this in succeeding generations, and the 
resulting plants recede in their characters more and more 
from A, and finally become almost undistinguishable from 
the good species which we have termed B or C. In this 
way it happens that we get plants which, though not quite 
agreeing in all respects with the essential characters of 
species, are very difficult to separate therefrom. 
Another difficulty that the student of willows has to 
encounter is that, since the flowers of most species come 
out before the leaves, and as it is desirable for a right 
understanding of the species to have specimens of both 
flowers and leaves, and as it is essential that these should 
both come from the same individual bush, great care has 
to be taken in securing specimens. 
From all this you will see that the willow-student has 
his work cut out for him, and it was with no little hesita¬ 
tion that for the purposes of the Flora of Perthshire I 
entered upon a studj- of the Perthshire willows. The 
work, however, had to be done by some one, and if I have 
learned nothing else, I have at least attained to an appre¬ 
ciation of the difficulty of the subject. 
Though I do not purpose on this occasion to lay 
before you the result of my investigations—nor indeed 
are these sufficiently advanced for that—I may men¬ 
tion that it is evident that Perthshire is very rich in 
forms, and that I believe I have several which are 
new to Britain. But in the hope that more specimens 
of it may be looked for and found, I wish to say 
a few words about the specimens which I now exhibit. 
These I found some years ago on Maol Ghaordie, a 
mountain which lies between Glen Lyon and Glen Lochay. 
The exact place I do not remember, but it is not impossible 
that the same form may occur on other mountains in 
Breadalbane. In the absence of flowering specimens there 
must be a little doubt as to the correct determination of 
these specimens, but I am strongly inclined to think that 
they may be referred to Salix spuria (Schleicher) Willd., 
which Wimmer and other authorities on the genus con¬ 
sider to be a cross between S. lapponum and S. arbuscula. 
That these specimens have much in common with these 
two species may be seen from the fact that having—before 
I commenced to study the willows—sent the specimens to 
Messrs Baker and Leefe, the two living British botanists 
who have made a special study of the genus, Mr Baker 
returned them as S. lapponum, and Mr Leefe as “ S. 
arbuscula ? or a form of S. phylicijolia." 
At first sight the specimens are on the whole very sug¬ 
gestive of S, lapponum, but on examination they will be 
found not to agree altogether with that species, but to 
