Oct. 28, 1886] 
limits. It would carry on in the Far East the work already 
performed in British India and Burmah. 
A SPANISH Expedition under Capt. Cervera has been explor- 
ing Adrar in the Western Sahara. Capt. Cervera describes Port 
Rio de Oro, where he landed from the Spanish cruiser Zigera, 
as rather difficult of entry, but, once entered, as secure from all 
winds, with good anchoring ground, and from 10 to 30 metres’ 
depth of water. ‘‘ Rio de Oro” is a misnomer, as there is only 
one well of fresh water, and that very dirty. There are, how- 
ever, good wells in the interior, and at four days’ journey there 
is arunning spring. The Expedition proceeded, between lati- 
tude 22° and 23°, south-eastwards 425 kilometres through an 
arid country of gneiss and granite, and struck the boundary of 
Adrar. The population is composed of four tribes—the Uled 
Delim, speaking and nearly all capable of writing pure Arabic, 
mixed with a few words of Berber origin. These tribes are 
nomadic, moving their tents from well to well for the pasture of 
their dromedaries, goats, and sheep. The capital of Adrar is 
Aatar, not Wadan, as hitherto believed. Wadan lies more to 
the south. 
“HYBRID” WHEAT 
ie is probably not generally known that the cereal from which 
we obtain our bread corn is almost invariably self-fertilised 
in nature, and that only a skilful expert can perform the delicate 
operation involved in the cross-breeding of wheat. The anthers, 
when near maturity, must be removed from a number of wheat- 
flowers, and on the following day the pollen of the male parent 
must be placed on the stigma. The opening of the glumes, 
however, is dependent on the swelling of the ‘‘ lodicules,” which 
only occurs when the temperature of the atmosphere is not less 
than about 75°. Below that minimum the florets will not open 
so as to expose the reproductive parts to the operator. The 
angle of opening of the glumes corresponds to this swelling, and 
when fertilisation has been performed the lodicules shrivel up 
and the glumes again close over the pistil, It had long been 
obvious that half a dozen different varieties of wheat, blossom- 
ing at the same time, may be grown in adjacent fields or in con- 
tiguous rows without the occurrence of interbreeding, in spite of 
the clouds of pollen which sunshine and warmth develop at the 
time of blossoming ; and considering the remarkable results 
from the cross-fertilisation of numerous plants in gardens, it 
seems surprising that the same process should not have been 
applied to wheat. Many years ago a well-known selector and 
‘*improver ” of cereals, the late Mr. Patrick Sheriff, tried some 
experiments in this direction. His usual method of improve- 
‘ment consisted in the selectim and careful cultivation of 
“sports,” and he was approaching the end of his career when 
his earliest attempts at cross-breeding were made. The in- 
creased vigour of wheat, the moulding of the ear, the produc- 
tion of a larger and fuller ear, with superior grain, earlier 
maturity, and the modification of the straw so as to render it 
stronger, or shorter, and less liable to become laid as in the 
present season, are all improvements which may certainly be 
accomplished in regard to this cereal, just as analogous modifi- 
catioas have beeen effected in animals and some other plants by 
the recognised methods of breeders. 
The wheat-crop of the United States reaches at present 
50,000,000 quarters, or four times that of England, and this may 
in some measure account for the numerous experiments in cross- 
breeding by scientific American farmers, and especially by some 
of the professors of agriculture in the colleges of that country. 
The same remark applies to France, where the cultivation of 
wheat is relatively far more important than in England, and 
where the noted seed-firm of Vilmorin are now in the midst of 
the work of cross-breeding. But even in England, disheartened 
as farmers may be as regards wheat-culture, their prospects 
might certainly be improved if the average production of this 
cereal could be increased, its quality improved, and its liability 
to disease and injury from indifferent weather diminished. Both 
growers and consumers, therefore, have an interest in the under- 
taking of Messrs. Carter and Co., the seedsmen, who for several 
years past have been engaged in the cross-breeding of wheat at 
their trial-grounds and gardens at Forest Hill. The collection 
of different sorts of wheat at this establishment includes varie- 
ties from every country which exports this grain to England. 
Some of them are not hardy, and the wretched appearance of 
the growing specimens of Persian and Indian varieties was 
NATURE 
629 
probably due to their depreciation in our climate. Some of 
the colonial and other sorts were excellent, but none could 
compare to the so-called hybrids. 
The operations commenced in 1882 by the sowing of a num- 
ber of the best English and American varieties, and in the 
following summer twenty crosses were effected by experts who 
are usually employed by the firm in delicate manipulations of a 
similar kind in connection with garden vegetables and flowers. 
In the following autumn the hybrids, as they are usually called 
for convenience, were sown between the rows of the male and 
female parents for the sake of comparison, and in the succeeding 
year the mixture of the breeds became apparent. In one plot, 
for example, the female parent was a short-strawed velvet- 
chaffed variety, and the male a very large, bearded, and tall 
American wheat, and the offspring attained a stature exceeding 
that of the former by a foot, with smooth chaff, and stout thick- 
set ears bearing minute awns at the apex of the chaff of each 
grain. This last-named peculiarity, the occurrence of defensive 
points in serrated order from top to bottom of the ear, may be 
referred to as one of the many advantageous peculiarities which 
have been developed in the course of the experiments, and it 
has gained for the new variety the appropriate name of ‘* Bird- 
roof.” 
2 Another of the cross-breeds, having the earliest of English 
varieties, Talavera, for one of its parents, was almost ready for 
cutting this year on July 21, when we inspected the new sorts, 
a very early date in the case of a late backward harvest. 
Another has the grains very firmly set, and therefore not liable 
to shell out even when the crop is dead ripe, as it usually is 
before the time of cutting in New Zealand, where this wheat 
will probably prove popular. 
Another of the crosses proved to be a wheat with shorter 
straw than any other variety in cultivation, and this too will 
prove a valuable modification, since neither soil nor season, 
however productive of straw they might be in certain years, 
could throw the crop down. Now does it surprise the experts 
that the offspring of two parents which are both of average 
height, should prove to be a dwarf in regard to the length of 
its straw, since they have had occasion to observe the same 
thing in the breeding of peas—two sorts of peas, each 4 feet 
high, and requiring the support of sticks, having produced a 
very useful seedling of 23 feet, which requires no such artificial 
assistance. 
We cannot attempt a detailed description of the numerous 
other peculiarities—some of them promising to be highly 
advantageous—which have been developed in the course of 
these wholesale experiments. But we may here observe that 
the most tiresome part of the business has proved to be the 
fixing of the types after the crossing had been accomplished. 
The work, however, has proved sufficiently successful to en- 
courage the experimenters to undertake the cross-breeding of 
barley as well as wheat, and to lead them to anticipate a large 
demand for their new varieties, not only in this country, but in 
the colonies. H. E. 
DR. AUGUST WEISMANN ON THE IMPORT- 
ANCE OF SEXUAL REPRODUCTION FOR 
THE THEORY OF SELECTION 1 
N Nature, vol. xxxiii. p. 154, was given an article on Prof. 
Weismann’s most interesting and important memoir on 
‘The Continuity of the Germ-Plasma considered as the Basis 
of a Theory of Heredity.” The present memoir also abounds 
with interest, and may be regarded as following naturally from 
the former one as a continuation and further elaboration of some 
of the questio s raised in it. The main aim of the inempir is 
to establish the position that the process of sexual reproduction 
is the prime agent by which all the varied differentiations of the 
complicated phyla of the Metazoa has been brought into exist- 
ence. A strong part of the argument is devoted to the esta- 
blishment of the position that peculiarities acquired by the 
parent are not transmitted to the offspring, and to showing that 
the hypothesis that such acquired peculiarities are transmitted 
is not necessary for the explanation of the known phenomena of 
heredity and the mode of origin of the series of organic forms. 
It will be remembered that the assumption of this position 
forms an important and necessary factor in the theory of the 
“Die Bedeutung der sexuellen Fortpflanzung fiir die Selektions 
Theorie.”” (Jena: G. Fischer, 1886.) 
