president’s address. 
13 
from the Arum would not affect the Garlic. They were at the 
time, and are still considered to be species. More recently 
Mr. Soppitt found that the cluster-cup on Lily-of-the- Valley has 
its Puccinia upon Phalaris, the spores of which closely resemble 
the two above-named species. From a number of experimental 
cultures on the part of Mr. Soppitt, many of which I repeated 
and confirmed, it is clear that the Puccinia on Phalanx which 
originates from the Lily-of-the-Valley cluster-cup, will not give 
rise to the cluster-cup on Arum, nor on Allium, and vice-versa, 
the Arum and the Allium cluster-cups will not give rise by 
their respective mildews to the Lily-of-the- Valley cluster-cup. 
It is clear, therefore, that we have here to do with distinct 
biological species. To take one more case — the Dodder. Are 
the different forms of this plant to be called distinct species 
because they grow upon different hosts ? Most people will consider 
that they should not, as the external or morphological differences 
between them are practically nil. But the Dodder is essentially 
a parasitic plant, — it can exist in no other way ; and if it can be 
shown that the Dodder on Clover will not and cannot be induced 
by any means to grow upon Nettle, and the converse, I am 
inclined to regard them as distinct biological species. To take an 
illustration : I have been familiar with the plants upon a certain 
heath in West Norfolk, viz., North Wootton Heath, since my 
childhood. I received my first lessons in botany upon it, and one 
knows how tenacious are one's early impressions. Now the Dodder, 
the Ling, and the common Whin, are all three abundant upon 
North Wootton Heath, but never from the year 1858, when 
T gathered my first botanical specimen, down to 1895, have I ever 
seen the Dodder on any other host than the Ling upon this heath. 
A few years ago 1 saw for the first time in Norfolk the Dodder 
hanging in rich festoons on the Whin bushes at liunton, near 
Sheringham, and had I been able as I had intended, to have 
taken part in the excursion last year to this place, it was my 
intention to have made a careful search to see if it occurred 
there upon the Ling as well, which quite possibly it does. But be 
that as il may, I think that if the species at 'Wootton be the same 
