October, 1908. j 



865 



SCIENTIFIC AGRICULTURE. 



PLANT EXCRETA. 



Popular opinions generally have some 

 foundation in fact, whether or not they 

 may seem reasonable on a careful an- 

 alysis. It is said that certain plants 

 poison the land and this has led to the 

 belief that certain plants will excrete 

 matter into the soil that will be in- 

 jurious to other plants. Referring to the 

 current belief, Prof. Clinton D. Smith 

 recently answered a correspondent in 

 the Countvy Gentleman to the effect 

 that the probable reason of the lack of 

 fertility in certain soils, once fertile, is 

 not so much the lack of plant food, or 

 soluble plant food, as the presence in 

 the soil of certain bodies, partly known 

 and probably others unknown, which 

 are poisonous to the growing cop. It is 

 also believed that the source of these 

 poisonous bodies is the previous crop, or 

 crops. A German scientist, after a 

 series of extensive experiments, believes 

 that plants excrete potash, as certain 

 ripe crops contained a great deal less of 

 it than the same crops when sending 

 forth vigorous shoots in the early part 

 of their growth. 



On the other hand, the investigations 

 in plant physiology during the last ten 

 years have led to the present belief that 

 the plants are much like any other 

 animal possessing life, but, by their 

 method of life, are ordinarily held in 

 situ, growing in the land jnst as oysters 

 and sponges do in the sea. These living 

 things, growing in the land, are presumed 

 to take their food, water and oxygen 

 through the roots and are presumed to 

 exhale any resulting excreta through 

 their leaves. The carbonic dioxide, or 

 carbonic acid coming from the leaves of 

 plants is presumed to be similar to the 

 carbonic acid exhaled from animal 

 lungs. If these conclusions be correct 

 and if every plant or sponge is but a 

 humbler member of the great living 

 animal world, we can see at once that 

 we have yet very much to learn con- 

 cerning plant biology. If with our quick 

 American appreciation of new ideas, we 



take hold of thi s matter in earnest, a 

 we now seem to be doing, the benefit to 

 the agricultural interests of the United 

 btates will be large, far beyond our 

 present comprehension. 



We who live in the alluvial country, 

 with low lands necessitating careful 

 drainage, can quickly perceive that if 

 sugar cane is an air-breathing plant, as 

 it must be, and if the air it breathes 

 must be inhaled through its roots before 

 it can be exhaled by the plant through 

 its leaves, the earth in which the cane 

 plant grows must be permeated by 

 atmospheric air sufficiently to give the 

 plants their necessary oxygen. The 

 sugar cane is not an aquatic plant. It 

 cannot get its oxygen out of the water 

 as fishes do, and, on the otlier hand, 

 water in undue quantity drowns these' 

 dry-land plants. 



It is less than twenty-five years ago 

 that Helriegel brought out in Germany 

 and definitely formulated the now 

 generally accepted theories of the value 

 of leguminous plants, such as cow peas, 

 alfalfa and clover, in fertilizing land by 

 the accumulation therein of nitrogen, 

 which nitrogen is secreted from the air 

 by the bacilli that make the roots of 

 these ; plants their habitat. The Old 

 Roman and Greek world knew the 

 advantage of leguminous plants in a 

 rotation of crops, but never ascertained 

 the reason Avhy such plants were so 

 valuable as a fertilizing agent. In plant 

 physiology we understand that until 

 within ten years it was thought that 

 plants exhaled carbonic acid and inhaled 

 oxygen and all this through the leaf 

 system. This belief is now apparently 

 dissipated and we find the plants lining 

 up with the rest of the living things of 

 the world, inhaling their oxygen and 

 ingesting their nutriment through one 

 set of organs and exhaling any necessary 

 excreta through other organs. As to 

 the excreta of plants in the soil and the 

 poisoning of the soil therewith, we are 

 still very much in the dark, as all this 

 world seems to indicate.— The Louisiana 

 Planter & Sugar Manufacturer. Vol 

 XXXX, No 25, June, 1908.) 



