u8 PLANT PHYSIOLOGY 



the matter by some practical work, which he may do along the 

 following lines: 



Suggested Experiments. Procure two pots of soil from ground known 

 to produce good crops of green peas, and thoroughly sterilize one of them 

 by steam (to kill all bacteria). Then plant in each the same number of 

 good seeds of green Peas, give them favorable conditions for growth, and 

 observe results. Finally examine the roots for the presence of nodules. If 

 practicable apply bacteriological examination of these. 



Procure two similar pots of soil, and thoroughly sterilize both. Then 

 to one add a culture of Pea-form of bacteria such as is issued for experi- 

 mental purposes by the Department of Agriculture; plant in both equal 

 numbers of similar Peas, give proper conditions for growth, and observe 

 results. 



The action of these bacteria raises a question as to the pres- 

 ence of such forms in the soil, and this in turn suggests an 

 inquiry as to the various methods by which soils receive their sup- 

 flies of combined nitrogen, that is, how soils are nitrified. Upon 

 this very important matter, so important from an economic as 

 well as a scientific standpoint, the student should now acquire 

 information and express his results in a proper exposition. 



Finally, under this subject, we have to take account of those 

 curious cases in which some plants obtain their nitrogen in the 

 form of compounds from other plants. This is done to some 

 extent by all parasites, but it is especially peculiar to the Insec- 

 tivorous Plants, whose ecology the student should here consider. 

 This animal-like acquisition of combined nitrogen brings up 

 also the consideration of the acquisition of combined nitrogen 

 by animals, their sources of supply, their conservation or other- 

 wise of it, and this the student should also consider. 



So much for the absorption of nitrogen; we turn next to the 

 sulphur and phosphorus. Our knowledge of their utilization, 

 however, aside from the mere fact that they are derived from 

 the sulphates and phosphates of the soil, is extremely scanty; 

 and the experimental difficulties of the subject are so great that 

 the student must be content to work it up through the literature. 



Nomenclature of Proteids. As this work is in press, there has 

 appeared an important report, by a committee of chemists, upon proteid 

 nomenclature (Science, 27, 1908, 554), the most striking recommendation 



