CEdema of the Tomato. 125 



unequal operation of the natural forces which are associated in the 

 etiology of this most interesting phenomenon in abnormal plant devel- 

 opment. To fully carry out this would lead the present writer too far 

 afield at this time upon an inquiry into the operation of the laws of 

 plant growth under artificial conditions of environment. The subject 

 is none the less one of great importance both from a scientific and 

 economic standpoint, and deserves serious consideration. A student of 

 cryptogamic botany, and especially one who devotes any serious atten- 

 tion to the relation existing between mycology and plant pathology 

 cannot escape an inquiry into the pathological changes induced by the 

 action of a symbiotic organism,* or whether the symbiont merely takes 

 advantage of a low vitality or degenerate tissues introduced through 

 unfavorable surrounding conditions, or the unequal operation of physio- 

 logical laws. So much has been demanded of the writer by the present 

 case and until the investigation had been carried to the extent presented 

 here, it could not be said whether or not any symbiont stood in causal 

 relation to the trouble. 



To properly conduct the inquiry farther would necessitate a broad 

 treatment of the manifold related forces. Compartments should be 

 arranged so that the temperature of the soil and air could be controlled 

 independently. Several such compartments should be arranged to 

 maintain the soil at a given temjierature and vary the air temperature. 

 Several others with a given air temperature and varying soil tempera- 

 ture; variations also m the humidity of the air and moisture of the 

 soil, the latter as has been shown can be treated to control the trouble. 

 Studies with different kinds of soils would undoubtedly yield interesting 

 and important results, for clay soil as is well known is more retentive 

 of raoi-iture and would less readily yield its moisture to the roots. 

 Means for the artificial agitation and interchange of the air should 

 be jirovided. The inquiry should embrace studies of nutrition 

 and assimilation. The effect of artificial light should be studied 

 in connection with the trouble. Although some of the earlier 

 experiments, with the use of artificial light cast doubt f upon the 

 question of carbon assimilation under . such conditions it has 



* Symbiont here is used in the broadest sense of that term, which means a 

 common life for a greater or less period between two organisms. 



f DeCandolle, Memoires des savans etrangers de I'Institut des Sciences, T. 1, 

 1806, p. 333. 



Physiologie vegetale, 1832, T. 1, p. 131. 



Biot. Froriep's Notizen, xiii, 10, 1840. 



Herve Mangon, Production de la matiere verte des feuilles sous 1' influence 

 de la lumiere electrique. Compt. Rend, herb, d. Sci. Paris, 1861, T. hii, p. 243. 



