358 BOTANICAL GAZETTE [may 



as the root grows older, the oxidation becomes weaker (as shown by 

 the less intense coloration) and vanishes in basipetal order. The 

 short growing zone of the root between the root cap and the region 

 of root hairs shows very little if any oxidation. The cells of the root 

 cap behaved differently in different plants. In some there was a 

 very weak oxidizing power, insignificant in comparison with that 

 of the absorbing region of the root; in other plants the root cap 

 showed no power to oxidize. This observation is the more inter- 

 esting because Pfeffer 16 regarded the experiments of Moi.isch 

 to lack proof that the guaiac-bluing power was due to living cells 

 and not to the dead or dying cells of the root cap. 



The oxidation which occurred in naphthylamine and benzidine 

 solutions first appeared on the outer surfaces of the walls of the 

 root hairs and epidermal cells, later in the wall itself, and finally in 

 the outer layer of the ectoplasm. When roots were left for a long 

 time in a solution of these chromogens, the entire protoplasm of the 

 epidermal cells and root hairs gradually assumed the dark color of 

 the oxidized chromogen, although it was not determined whether 

 this color was due to the diffusion inward of the dye formed at the 

 surface, or to an actual intracellular oxidation. 



AND 



The experiments described in succeeding pages consisted in 

 studying the oxidizing power of wheat plants grown under various 

 conditions in connection with soil-fertility investigations. B *« 

 necessary to grow the wheat plants used for experimentation m 

 solutions, since in such cultures it is possible to observe the oxi 

 without disturbing the roots. For the study of soil condition 



*i f'tVi five r>3.rt - 



aqueous extract was made by stirring one part of soil wim r 

 of distilled water for three minutes and filtering after 30 m *^ 



rh a P^tPiir-rhQmWlQnH rlav tube. It has been foun 



throu 



ducin 



soil extracts prepared in this manner possess a plant- pro ^ 

 power similar to that of the soil from which they were ma e. 

 other words, fertile soils yield extracts which promote g 00 ^^ 

 growth, and infertile soils give extracts producing poor plant gr^ ^ 

 The water used in making solutions and soil extract w 



16 Abhandl. kon. sach. Gesells. Wiss. Leipzig, Math. Phys. U. is**u 





