SCIENCE- G OSSIP. 



in this particular respect that the study of the 

 chemistry of the soil yields the most important 

 results, and is. as it were, most fully justified. A 

 bulky tome might be devoted to the specific treat- 

 ment of this branch of the subject ; but in this 

 brief paper only a few points can be brought for- 

 ward. It is in the form of nitrate that potass, 

 calcium, and soda are most readily absorbed by 

 the plant so as to serve its nutrition. Thus white 

 or black mustard grown in pots in pure sand with 

 minerals, or in water culture, grew well and 

 developed completely when nitrate was added. 

 "With no nitrate the growth was feeble, and the 

 ■ water-cultured plants died. Grass, rye, etc., were 

 manured with nitrate alone, and again with kainite 

 and superphosphate. It was found that the nitrate 

 plots grew far more luxuriantly than the plots 

 without nitrate, although where phosphates were 

 absolutely wanting in the soil the nitrate manuring 

 did not produce any more nitrogenous matter in 

 the plant — i.e. the forcing action of the nitrates 

 hardly came in evidence if unsupported by phos- 

 phates. It would appear that the presence of 

 nitrate in the soil seems to enable the plant to 

 take up more nitrogen in other forms than when 

 the soil is left unmanured or is supplied with 

 sulphate of ammonia. The favourable action of 

 nitrate is evident in every stage of the develop- 

 ment of the plants, and they were always the first 

 to ripen. The influence therefore of the nitrates 

 of the soil, especially if supported by the phos- 

 phates, on the physiology of the plant seems 

 clearly demonstrated. 



It is known, moreover, that many plants can 

 store up an excess or reserve of nitrates in the 

 medullary parenchyma and the cortical parenchyma 

 of the stem, especially at the period immediately 

 before flowering, as if they were destined 'for the 

 special nutrition of the floral parts. This power 

 is. however, a special peculiarity of certain plants, 

 e.g. nettle, potato, dog's-mercury, mustard, spinach, 

 common cabbage. According to Berthelot and 

 Andre, nitrate of potass is universally present in 

 plants. It is mostly formed in the stem itself, not 

 in the soil or in manures, by cells which behave 

 like nitric ferment. It exists in the tissues of 

 most plants in such a proportion that it must needs 

 be formed in the tissues. The salts of potass re- 

 present the phenomena of oxidation, which occur 

 chiefly in the stem and the reproductive organs. 

 It must be observed, however, that for this extra- 

 ordinary and highly remarkable production of 

 nitrates within the tissues, special .microbes of 

 nitrification are absolutely necessary. The or- 

 dinary oxidation of the protoplasm or of its waste 

 does not proceed so far ; it stops short at the 

 formation of ammoniacal or amido-nitrogen com- 

 pounds, such as asparagine, glutamine, tyrosine, 

 etc. It is presumed, as a matter of course, that the 

 nitrifying- microbes which operate within the tissues 

 are derived and drawn in there from the soil. 



Other testimonies can be adduced relative to the 

 subject-matter of this paper. " The composition 

 of the soil," says Professor de Ville, ''influences- 

 plant-colour, size, weight, general aspect, the 

 amount of carotin and that of chlorophyll. Where 

 nitrogen predominates in plants, as in hemp, wheat r 

 etc., there is the least carotin and chlorophyll when 

 a manure without nitrogen is used. Where potass 

 predominates, as in potato, vine, etc., there is the 

 same effect when potass is suppressed. The colour 

 of the leaves before flowering remains green, or 

 turns yellow, according as the soil is wanting in 

 phosphate, in potass, or in nitrogen. In plants 

 which particularly require nitrogen, the leaves- 

 turn yellow in its absence. Both chlorophyll and 

 carotin are most intense with full nitrogen. Without 

 minerals both tones are lowered, but not so far as 

 without nitrogen." M. Edmond Gaine states that 

 " a high comparative moisture in the soil accelerates- 

 the growth, especially of the stem and leaves. 

 Inflorescence is retarded either by dry soil or by" 

 moist air, and is hastened by moist soil and dry air r 

 especially the latter." It may be interesting to- 

 add that dryness of the soil lessens the number of 

 the inflorescences, the number of flowers in each 

 inflorescence, the number of seeds in each fruit and 

 on each plant. On the other hand, it increases the 

 number of the ovaries and of fertile ovules in each 

 of the inflorescences. In some, or perhaps in most 

 cases, the number of the fruits which reach 

 maturity, other conditions being favourable, is 

 nearly the same as that of the flowers in a dry soil,, 

 and only about one-half thereof in a humid soil. 



At first sight it might seem that all these most 

 important and interesting reactions of the mere- 

 physical conditions or properties of the soil upon 

 the organs of the vegetable were, so to speak,, 

 purely mechanical ; but, as a matter of fact, they 

 are so only indirectly. The direct residt is a 

 purely chemical effect — that is to say, it is chemical 

 stimuli induced and brought into action by the 

 flow of plastic material, owing to the moister con- 

 dition of the tissues growing in a humid soil, or 

 vice versa in a dry soil. Thus, for instance, in the 

 researches of M. Prunet on the potato tuber it was- 

 observed that the distribution of the immediate- 

 principles — starch, &c. — and of the mineral matters- 

 of reserve in the different regions of the tuber, is 

 much more uniform in a humid, and more diverse 

 according to the region in a dry, soil. It is not r 

 of course, insisted that humid conditions are 

 physiologically more favourable to annuals and 

 perennials than droughty conditions. The effect 

 of the former is to arrest physiological differen- 

 tiation ; the latter accentuates it, and so not 

 merely prolongs the individual career (oaks live- 

 one-third as long again in a dry soil), but also 

 ameliorates the quality of its offspring, the seeds. 



Pattcrdalc, Westmorland. 



ERRATUM. — Bead at p. 99, mitt, bottom of second 

 column, MelqpJiagus ovimis for Ixodes reduviiis. 



