154 REPORT OF THE CONFERENCE ON GENETICS 
perfume, diffused by the catkins at the time of the ripening of the 
anthers. 
The species of Saliz whose flowering season is very early are visited 
by a great number of insects. 
When hybridisation takes place between two quite distinct species, 
several intermediate, fairly definite, forms are produced. It is not 
unusual to find individuals of which the branches at the bottom and the 
sterile branches show by their foliage a very marked dimorphism. The 
capsules of the hybrids appear in many cases to be almost normal ; they 
enclose numerous seeds which may possibly germinate. On the other 
hand, there are produced ternary hybrids which prove the fertility of the 
seeds, or at all events of some of them. 
In dwarf willows or in certain forms derived from Salix nigricans, the 
style is often atrophied. The proportionate length of the style is not at 
all fixed. Itis clear that two species having the style short or almost 
absent will never produce a species with a long style. Willows are 
frequently planted, consequently the parents must be lacking in the 
vicinity, if varieties do not appear spontaneously. 
Populus.—My excellent friend M. Dode, who is preparing a monograph 
on the genus Populus, declares that hybridisation is almost as common in 
this genus as with willows. 
PotamME®. Potamogeton.—Hybridisation fairly frequent. Results 
fairly numerous; relative sterility. 
ORCHIDE®.—We know how orchids lend themselves to hybridisation. 
Crossings take place even between species of incontestably distinct genera, 
such as Serapias and Orchis. 
I will not go into all the well-known causes which facilitate cross- 
fertilisation. I will simply mention that the organ which appears the 
most unchanging, and in consequence is frequently a sure guide in 
determining one of the parents, is the gynophores (gynostéme). The 
form of the spur comes next in order of stability. The form of the lip 
(labellum), and above all the colour, ave very variable points. Hybrids 
which have been formed in marshy fields have persisted for several years 
after a drainage which had dried up the locality and swept away one of 
the parents. The hybrids have not been reproduced on the spot, but 
they have been multiplied through their bulbs. For several years I haye 
kept hybrids in pots, reproducing themselves by bulbs, and I have only 
observed variations of colour with a tendency to degenerate. 
As to Cyperacee, Graminee, Filicinee ; recent observations relating 
to these have demonstrated the frequent action of hybridisation. It is, 
however, difficult to generalise with the limited materials at our disposal. 
[(Nortr By THE Eprtor: Monsieur Camus laid before the Conference 
an Analytical Catalogue of Spontaneous Hybrids of European Plants, 
containing the original bibliography, the synonyms, the geographical 
distribution, and the herbarium notes relating to the hybrids—a work on 
which he has been engaged for upwards of thirty years. Whilst fully 
recognising the immense value of this catalogue and the really wonderful 
patience, investigation, and research which it displays, we are of opinion 
that it is too long to be embodied in a Report of the Conference and merits 
publication as a separate volume.—W.W.| 
