44 



BOTANY. 



Plants having a root system in comparatively dry ground absorb their 

 liquid food through root hairs and roots. 



Aquatic plants (plants in water) absorb liquid food through nearly the 

 entire surface in contact with the water. 



The plant food must be in a very dilute solution; a strong solution injures 



the plant, and, if too strong, 

 will kill the plant, because 

 by the law of diffusion the 

 water in the plant is removed 

 to such an extent that the 

 plant becomes flabby, and if 

 turgor is not restored, the 

 plant will die. 



Soil which is not saturated 

 with water, i.e., that which 

 is only moist, or even which 

 may seem dry, still contains 

 water which forms a thin film 

 (capillary film) around the 

 soil particles. 



The root hairs become 

 firmly fixed to certain of the 

 soil particles and are thus 

 brought in close contact with 

 the water film which contains 

 mineral and nitrogenous food 

 in solution. This film is con 

 tinuous from one soil particle 

 to another in soil of the right texture and physical properties, and thus as 

 the root hairs absorb that portion of the film in contact with them, by capil- 

 larity the film draws more water through the soil from moist places. 



Materials:— Potassium nitrate, sodium chloride, calcium sulphate, mag- 

 nesium sulphate, calcium phosphate, for nutrient solution as per paragraph 

 68. A larger amount of potassium nitrate (saltpetre) for exercise 19. 



Wide-mouth bottles, or small crockery jars, with perforated corks to fit, for 

 the water culture. 



Seedlings started in a germinator. 



Seedlings, grown in pots, two or three weeks old, for exercises 17 and 18. 



One or more long potatoes ; sugar. 



Microscope, etc. Razor. 



Fig- 33- 



Pot in which the 2% solution was poured. 

 After four hours a 556 solution of potassium ni- 

 trate was added. This caused two of the seed- 

 lings to collapse after about ten hours. Photo- 

 graphed eighteen hours after last application. 



