Jury 27, 1899] 
NATURE 
397 
Partial Prepotency. —This not very happy title is given by Mr. 
Hurst to a law which he puts forward as explaining, at least so 
far as the genus Paphiopedilum (= Cypripedium) goes, the varied 
results in the inheritance of characteristics. The law one takes 
to mean that in one part of an individual hybrid the mother, 
say, is seen to be prepotent ; in another individual the same 
structure is inherited from the father; while in a third both 
parents are represented by an intermediate form of the special 
feature under consideration. We are then asked to imagine a 
real case where the combinations and permutations of all the 
component structures must be reckoned with. No doubt this 
brings the possibilities for variation very forcibly before us; but 
surely it is only giving another name to what must be expected 
whenever two parents representing two strains produce young. 
Although Prof. Ewart’s zebra hybrids were mentioned by Mr. 
Hurst in another connection, yet little heed was given by any 
one to the possibilities of hybrid plants throwing back to an- 
cestors in the dim past, as undoubtedly appears to be the case 
with. animals. 
Prepotency of Varieties, Species, and Genera.—Mr. Uurst’s 
paper, which, indeed, was the only one that in any way system- 
atically attacked the broad headings of hybridisation, contained 
much information deduced from the Orchidee as to the inheri- 
tance by hybrids of the characters which are commonly valued 
as varietal, specific and generic. As might be imagined, the 
generic are most difficult to efface ; the specific again are less 
lasting but more persistent than varietal, which are fleeting. Mr. 
Hurst had, however, to allow that distinct variations may 
transmit their qualities, and it would be difficult for him to do 
otherwise in the face of Mr. Bateson’s examples; he gave ex- 
ceptions, which he said are by no means rare—these come in 
when the variations are slight or the ancestry variable, and an 
abnormality he found to be transmitted either wholly or not at 
all. The case given by Prof. Hugo de Vries of the twisted 
variety of teasel (Dipsacus sylvestris) when crossed with Dzpsacus 
fullonum being prepotent as regards the abnormality, exempli- 
fies the former of these two alternatives. Prof. de Vries, it 
should be called to mind, explains it as a case of pangenetic 
infection. Finally, Mr. Hurst said that when the same vari- 
ations are found in both strains, they may be traced in the second 
or following generations, but seldom otherwise. Prof, Vries’ 
second experiment is at first opposed to this ; but the latter stage 
confirms it. He desired to obtain artificially a hairless variety 
of Zychnis diurna, similar to one found in nature, and known as 
L. presti. To do this he crossed the ordinary hirsute variety 
with his glabrous form of L. vesfertina already mentioned, and 
the hybrids were all uniformly hairy. The offspring of these 
again showed the characters of one or both parents in all de- 
grees. Taking two glabrous examples and crossing them, a 
constant variety of Z. dzurna without hairs was forthwith 
obtained, starting with a batch of 390 plants, all glabrous. 
Parthenogenesis and Polyembryony.—Prof. Henslow, among 
the many interesting details which he contributed, mentioned 
how pollen tubes are sent out even when the pollen of a pea is 
placed upon the stigma of a lily, and how on more nearly allied 
forms, although no fertilisation may take place, yet the irrita- 
tion is enough to cause the empty ovary to swell and appear to 
contain seeds in a way comparable to the formation of galls 
(partial hybridisation). To explain cases where in crossing a 
species of one Orchid genus with others, e.g. Epzdendrum with 
Cattleya, Laelia and Sophronites, the first was completely pre- 
potent, Mr. Hurst advanced the theory that the occurrence 
was due to a kind of parthenogenesis, the pollen encouraging 
the egg-cells to develop into seeds without absolutely having 
the power to fertilise them. 
A difficulty met with in the raising of hybrid races of oranges, 
which Mr. Webber described, is due to the fact that in the genus 
Citrus, adventitious embryos arise from the cells of the nucellus 
outside the embryo sac containing the normal egg. The result 
is that the latter only is affected by pollen, and from the seed 
arise several seedlings as shown in lantern pictures, only one of 
which can be the hybrid, the others reproducing the mother 
plant exactly. 
Vigour.—The exceptional growth of hybrid plants being a 
well-known phenomenon was referred to again and again, and 
was put down by Mr. Hurst to the effect of out-crossing, as in- 
breeding he found in his experiments reduced the vigour 
at once. 
Diminution of Fertility.—Dr. Wilson’s results point to this 
being due to the poor development of pollen, and the lessened 
NO. 1552, VOL. 60] 
fertility of the male was shown by Mr. Hurst’s statistics for 
Paphiopedilum. Of crosses in this genus between pure species 
95°05 were successful ; hybrids fertilised with pollen from pure 
species produced seeds in 91°82 per cent. of the cases; while, 
pure species were only fertilised by the pollen from hybrids in 
60 per cent. of the experiments. The case of male elephants 
being usually sterile in captivity seems worthy of mention in 
this connection, Mr. Hurst's generalisation that diminution of 
fertility is due to conditions of life rather than to any difference 
in the form or constitution of hybrids gains support, which is 
added to by the evidence given above under the headings IT. 
(Specza/ cases) and III. 
Microscopic Structure.—Al\lusion was made to Dr. Macfar- 
lane’s work on the structure of primary hybrids, but what little 
was said about the microscopic conformation of secondary 
hybrids in Adéuca (Dr. Wilson), and in Rhododendron (Prof. 
Henslow in the discussion), points to their possessing no internal 
characters of the importance of specific ones. 
Hybrid Races.—That secondary hybrids differ more than 
primary ones from the parent species was the opinion of M. de 
la Devansaye and Mr. Hurst, and the latter speaker gave a 
series of figures showing the stability of the former kind ; for out 
of 500 seedlings of a hybrid Berberis, 90 per cent. reproduced 
the immediate parent form, while in no instance was there com- 
plete reversion to either of the grandparent species. It is 
possible that many of our so-called wild species are stable 
hybrid races. 
V. THE Economic SIDE OF HYBRIDISATION. 
Mr. Webber, in his remarks, and Prof. Bailey, in his paper, 
both told the same tale with regard to the United States. The 
bulk of the hybridisation on the other side of the Atlantic is 
carried on with a view to producing plants that will stand the 
particularly disadvantageous conditions of frost and drought, 
and so on, that occur in the wide tracts of land that must be 
cultivated, or to improving the yield or quality of special veget- 
able productions upon which many persons depend for their 
living. Ornamental hybrids are bought for the most part in 
Europe. The Government does a great part of the work of 
production, and the experiment stations carry out the work of 
testing new varieties, be they privately raised or otherwise, 
which at the same time allows the growers to see the value of 
the plants before they are distributed. Mr. Hays, in the dis- 
cussion with regard to the little benefit accruing in this country 
to the raiser of a new plant, pointed out the opportunity given 
in America by the system just described for the said plant to 
be taken up. The Rev. G. H. Engleheart, as an amateur, and 
Mr. George Paul, as a nurseryman, talked of legislation whereby 
some sort of copyright should be established in new varieties. 
Mr. Bunyard pointed out objections, and showed how a man 
might raise sufficient stock before parting with any to ensure a 
profit he had calculated beforehand. This presupposes a fairly 
large sale, and might not be possible to the grower in a small 
way of business. Mr. Engleheart also alluded to there being 
no book in which the scattered facts so useful to the hybridist 
had been brought together. 
Perhaps the time will come when there may be State author- 
ities in this country to consider the scientific side of horticulture 
(as well as entomology and fisheries) in a modern way. At 
present the annual examination of the Royal Horticultural 
Society, upon the results of which certificates are granted, in- 
cludes a theoretical test not only on the practical but on the 
scientific side. This certificate is the only recognised one which 
the gardener can obtain, and its value would be much enhanced 
if the examination were accompanied, or say followed, in the 
case of candidates who obtain a sufficient number of marks, by 
a practical examination in both branches of the subject 
WILFRED MARK WEBB. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE. 
Mr. W. A. Houston, has been appointed to the post 
of assistant lecturer in mathematics in University College, 
Liverpool. 
Tue Agriculture and Technical Instruction (Ireland) Bill was 
read a third time in the House of Commons on Monday, and a 
first time in the House of Lords on Tuesday. 
Tue University College School Magazine announces that Mr. 
R. Tucker, who has guided the mathematical fortunes of the 
