104 



dioxid are still smaller when the experiments are continued longer than 

 those of plants respiring in air which contains oxygen\ Since the 

 carbohydrates (starch, sugar) furnish the material for respiration, it 

 should be assumed from the above facts that these material contents of the 

 cell are made use of abnormally in the absence of oxygen. With Pfeffer- 

 respiration can be conceived of as a process set up by two dove- 

 tailing processes. The first is the intra-molecular respiration ascertained in 

 the phenomena of fermentation which Borodin^ named internal oxidation. 

 The second process, possible only with a supply of oxygen from with- 

 out, is the immediate further oxidation of the products of fermentation 

 in the moment of their production. If this last act, absolutely necessary for 

 the life of the cell, is suppressed, not only the zone of the trunk of the tree, 

 planted too deep and lacking oxygen, loses its respiratory material, that is, 

 always becomes poorer in reserve substance, but it also forms those products 

 which lead to decomposition and the death of the cell. Insufficient respir- 

 ation therefore is a necessary preliminary condition for the dying back and, 

 to the degree in which the buried part approaches the surface of the soil, 

 gradually getting more and more oxygen, the fermentation will become 

 weaker and weaker and pass over into the normal process of oxidation so 

 that decomposition gradually reaches its limit. It is thus only a question 

 whether the tree has the possibility of forming new roots in the soil above 

 these limits in order to meet the loss of water produced by the transpiration 

 of the foliage. The stunted production frequently observable in early years 

 disappears as the more plastic material can pass downward and be used for 

 the new structures in the wood ring of the trunk and the roots. The more 

 rapid the growth, the greater the energ}^- of respiration (as shown by Saus- 

 sure) and the more the flat new root body is reached by light, so much the 

 more will the production of carbo-hydrates and its absorption of oxygen 

 and production of carbon dioxid increase*. 



The behavior of the trees planted too deep or only partially buried de- 

 pends naturally upon their specific character. In willows and poplars, for 

 example, the part sunk in the earth may indeed be found to be dead, but 

 near the top of the soil, the decomposition appears to have been stopped. 

 Numerous adventitious roots have been formed from the tnuik which, some 

 time after the tree has been buried, starts a healthy development of the crown. 

 The tree is therefore saved if it is able to produce new roots quickly near 



1 Wortmann (Ueber die Beziehungen der intramolekularen zur normalen At- 

 mung der Pflanzen. Inauguraldissertatiort. Wiirzburg 1879) states, to be sure, 

 that the amounts of carbon dioxid are equally large in intra-molecular and normal 

 respiration; it seems to me, however, that the short duration of his experiments 

 also caused the observation of the after effects of a previous normal functioning. 

 He, himself, admits (p. 31) that in a longer period with no addition of oxygen a 

 smaller amount of carbon dioxid was produced by the plants under experimentation 

 than had been the case in the constant presence of oxygen. 



~ Pfeffer, Ueber das Wesen und die Bedeutung der Almung. Landwirtsch. 

 Jahrb. 1878. 



3 Borodin, Sur la respiration des plantes pendant leur germination. 



* Borodin, INIemoires de I'Acad. imp^riale des sciences de St. Petersbourg. VII 

 s6rle. 1881. 



