33Q 



NATURE 



\_August 2, 1888 



it otherwise, and did the first stages of division not occur in 

 unfertilized eggs, we should have supposed that the sperm-cell 

 present in the ovum, although in a resting-stage, had some 

 invisible influence over it. 



It was possible, however, to arrive at a decision on this point ; 

 ' for, although most Daphnidoe do not lay their eggs if copulation 

 does not take place at the time the eggs ripen, in one species 

 {Moina paradoxa), the extrusion of the ova occurs independ- 

 ently of copulation. We therefore isolated females of this 

 species which contained ripe eggs in the ovary, and examined 

 them when they had passed the eggs into the brood-chamber. 

 How great was our astonishment to find that these ova, killed 

 shortly afterwards, were already beginning to disintegrate, and a 

 cell corresponding to that which we had taken fjr the sperm-cell 

 was present in each of them ! At first we considered the 

 possibility of copulation having taken place before the females 

 were isolated, and of the retention of the sperm-cell, which had 

 become inactive, in the brood chamber. But sections which we 

 made through nearly ripe ovarian eggs showed us that the sup- 

 posed sperm-cell was already present in them. It was thus 

 proved that this cell which unites with one of the eight first 

 segmental cells (we will for the present call it the " conjugating- 

 cell," Copulationszelle) cannot be an ordinary sperm-cell ; and, 

 moreover, that, besides it, an active sperm-cell from the male, 

 which had previously escaped our notice, passes into the egg in 

 consequence of copulation. In fact, this true spermatic element 

 was found after renewed examination of old an 1 new series of 

 sections as an exceedingly small nucleus in the yolk-mass. It is 

 difficult to recognize, but nevertheless may plainly be traced 

 passing into the yolk, and finally uniting in the ordinary manner 

 with the nucleus of the ovum. 



Thus the impregnation of these ova is not exceptional, 

 inasmuch as a normal fusion of the male and female nuclei takes 

 place. But. besides this normal conjugation of sperm-nucleus 

 and egg nucleus, another fusion of cell-bodies and cell-nuclei 

 occurs between the enigmatical "conjugating- cell," present 

 already in ovarian eggs, and one of the eight first segmental 

 cells lying at the vegetative pole of the ovum. 



It will oe impossible to conjecture as to the meaning of this 

 process until we know definitely how the " conjugating-cell " 

 arises : at present we are not able to state anything about it 

 with certainty. 



We intend to continue our observations, and hope before very 

 long to have more to say on this subject. 



Freiburg i/B., July 12, 1888. 



HOW TO INCREASE THE PRODUCE OF 

 THE SOIL. 1 



f N this pamphlet Prof. Wagner distinctly asserts the power of 

 leguminous cultivated plants, such as peas, beans, vetches, 

 lupines, and clovers, to use the free nitrogen of the air for 

 pa rp vses of nutrition. As this conclusion is distinctly at issue 

 with the opinions of the Rothamsted school, it revives a question 

 of deep interest, the answer to which has varied with our know- 

 ledge from time to time. In the earlier days of agricultural 

 chemistry the " mineral theory " of plant nutrition was in the 

 ascendant. According to this theory the mineral, earthy, or ash 

 constituents were taken from the soil, while the gaseous, com- 

 bustible or organic portions of the plant were derived from the 

 air. As knowledge progressed, this somewhat bold and 

 sweeping generalization required to be modified, and the 

 most usually received view (in this country, at least) for some 

 time past has been that of the absorption of mineral matter and 

 nitrates from the soil, and of carbonaceous matter from the air, 

 and to a limited extent from the soil in the form of carbonic acid 

 gas in solution. It has been urged that proof is entirely wanting 

 of the alleged power of plants to take free or combined nitrogen 

 from the atmosphere, while the intense effect of nitric nitrogen 

 upon growing crops, when added to the soil, has amply proved 

 that the soil is a source of nitrogen, and, according to received 

 views, the chief or only source of nitrogen to growing crops. 

 The results obtained by Sir John Lawes, Dr. Gilbert, and Mr. 

 Warrington at Rothamsted, upon the cultivation of red and 

 Bokhara clover, have been considered as proving that the 

 source of nitrogen in these plants was not the atmosphere, but 



1 "The Increase in the Produce of the Soil through the Rational Use of 

 Nitrogenous Manure." By Prof. Paul Wagner, of Darmstadt. Translated 

 toy George G. Henderson. (London : Whittaker and Co., 1888.) 



the soil and the subsoil, the plants having been found to send 

 down their roots some fifty-four inches in depth into sections of 

 the soil which, although out of reach of most cultivated plants, 

 were able to yield sufficient nitrogen for the uses of these 

 nitrogen-loving plants. Collectors of nitrogen these plants are 

 allowed to be by all, but at Rothamsted the collection is con- 

 sidered to be carried on in the deeper layers of the soil, and not 

 to extend above ground. Prof. Paul Wagner declares that 

 cultivated plants may be properly divided into nitrogen collectors 

 and nitrogen consumes, or as we might put it, into nitrogen 

 savers and nitrogen wasters. In the first class are arranged the 

 various members of the Leguminosas already named. At a 

 certain stage of their development these plants acquire the power 

 of taking all their nitrogen from the air. They thus become a 

 means of securing fertilizing matter from a free source, and are 

 therefore profitable. In the second class are placed the cereals, 

 grains, turnips, flax, &c, all of which are able to take next to 

 nothing from the store of nitrogen in the air, but which waste 

 the nitrogen of the soil, and must take from it, in the form of 

 nitrates, all the nitrogen they contain. In the pamphlet under 

 notice no proof is adduced for these views, but reference is made 

 to the detailed investigations carried out by the author. Hellriegle, 

 and E. von Wolff. These views must be considered as reactionary 

 and startling, and as diametrically opposed to the current of 

 opinion in this country for some years past. 



It is not to be wondered at that Prof. Wagner should give 

 considerable prominence to a feature in agricultural practice 

 which has almost entirely disappeared — green crop manuring. 

 If clovers, lupines, and vetches, extract their nitrogen from the 

 supernatant aerial ocean, and are able to supply upwards of 180 

 pounds of atmospheric nitrogen per acre per annum continuously 

 for a period of three years, no easier system could be devised for 

 obtaining the necessary nitrogen for fertilizing purposes. All 

 that is required is to secure the full development of the nitrogen 

 collector by supplying it with sufficient water, sufficient phos- 

 phoric acid, potash and lime, so that it may exert its powers 

 upon the constantly passing stream of air — it then provides 

 nitrogen for itself. What is this but a re-statement of the old • 

 mineral theory applied especially to the Leguminosre? 



Prof. Wagner's views upon the absorption of atmospheric 

 nitrogen and his consequent recommendation of green crop 

 manuring, are the two principal features of this little work. In 

 some places the German fault of verbiage is only too evident — 

 whole paragraphs being devoted to what is perfectly self 

 evident. Still, various practical suggestions of great value are 

 made. The remarks upon the proper method of applying 

 nitrate of soda are particularly worthy of attention. The effect 

 of this active manure in developing stem and leaf rather than 

 flower and fruit is acknowledged, but only as a consequence of • 

 the period of the plant's growth when it is applied. 



Nitrate of soda enables the plant to seize upon the stores of 

 phosphoric acid, potash and lime in the soil, and the effect is 

 rapid growth. This effect is however short lived, as the nitrate 

 is freely movable in the soil, and readily finds its way to lower 

 sections when it is no longer available. The case is therefore as 

 follows : — Nitrate of soda applied in February, March, or April, 

 is employed in the development of leaf and stem, and by the 

 time the period has arrived for grain formation it is spent. If 

 the same dressing had been applied later in the history of the 

 crop, and at the time when the embryo grain was being formed, 

 the same stimulus would have been given towards grain forma- 

 tion, which under ordinary circumstances takes the form of leaf 

 and stem development. The practical recommendation based 

 upon the consideration is to apply one-sixth part of the applica- 

 tion in autumn, two-sixths in March, and the remaining three- 

 sixths in May. The plant is to be fed during its whole life, 

 and not only at the period when it is forming leaves and stem, but 

 especially at the important period when it is forming fruit. The 

 remarks upon the ripening effects of superphosphate upon root 

 crops are also well worthy of attention. Excessive quantities of 

 superphosphate hasten too rapidly the processes of maturation, 

 and tell against prolongation of growth into the late autumn, and 

 this, it is submitted, accounts for the occasionally smaller results 

 obtained by the use of phosphates inla-ge quantities as compared 

 with those produced by more moderate dressings. 



Prof. Wagner comes to the conclusion, which we quite agree 

 in, that nitrogen, phosphoric acid, and potash are the principal 

 elements of fertility that require to be added to soils. The 

 remaining essential substances, although equally important to 

 the well-being of the plant, are usually present in ample quanti- 



