86 



BOTANY. 



plants are. The evaporation of water is probably as rapid 

 in hysterophytes as in holophytes of equal structural com- 

 plexity and similar habits. The fungi quickly lose their 

 water and become wilted and dried up when their supply 

 of moisture is cut off. On the other hand, among the 

 flowering hysterophytes the absence or small size of the 

 leaves greatly reduces the amount of evaporation. Clearly, 

 also, the respiration of hysterophytes is less than in holo- 

 phytes, there being little or no absorption of carbon di- 

 oxide. Oxygen, however, is absorbed, and carbon dioxide 

 excreted, by most if not all hysterophytes. 



Practical Studies. — (a) Germinate seeds of cabbage or radish on 

 moist cotton cloth, and examine the organs for the ab- 

 sorption of liquids (the roots), noting especially the 

 root-hairs on their surface. 



(J) Germinate several kernels of Indian corn in 

 moist sand, and when the roots are two to four cen- 

 timetres long transfer the plants to wide-mouthed 

 bottles or jars, supporting them as in Fig. 48. Fill 

 one of the jars with pure (distilled) water; fill a second 

 with well-water (which always contains many, if not 

 all, of the materials of plant-food) ; fill a third with 

 water from a stream or pond (which also always con- 

 tains all, or nearly all, the materials of plant-food). 

 Notice that the plants will grow in all the jars, as all 

 are supplied with carbon dioxide and water, the most 

 important plant-food ; but the best and longest con- 

 tinued growth takes place in the second and third jars, 

 (c) In case the materials can be obtained, fill a fourth 



water^cTilture J*"" (^^ '" '^^^ previous experiment) with a solution of 



experiments, the following constitution: 



Distilled water 1000 cubic centimeters 



Potassium nitrate 1.0 gram 



Sodium chloride 0.5 " 



Calcium phosphate 0.5 " 



Calcium sulphate 0.5 " 



Magnesium sulphate 0.5 " 



With this solution perfect plants may be grown, if care be taken 

 to renew the solution from time to time. 



Fig. 

 S h o w i n _ 

 method of 



