500 MANUAL OF BOTANY 



been found that the mucilage contams various substances which 

 the antherozoids seek. In the case of the Ferns, and some Sela- 

 ginellas, it has been determined that the attractive body is malic 

 acid. When a capillary tube containing a weak solution of this 

 substance is inserted into water containing some of the anthero- 

 zoids, they make their way very quickly to the orifice of the 

 tube. In the case of Mosses the attractive substance is cane- 

 sugar. That there is a definite attraction appears from the fact 

 that strong solutions of either acids or alkalies are avoided by 

 them with equal earnestness. 



A similar behaviour marks the plasmodia of certain of the 

 Myxomycetes. They move slowly towards a watery extract of 

 tan, but retreat from a solution of sugar, glycerine, or certain 

 neutral salts. Similarly, the zoospores of Saprolegnia are 

 attracted liy a solution of extract of meat. 



The sensitive tentacles of Drosera can respond not only to 

 contact, as before mentioned, but also to various substances 

 placed upon the leaf. They are easily induced to bend by drops 

 of liquid containing proteid matter, such as solution of albumen, 

 or milk. Certain inorganic salts, notably carbonate of ammonia, 

 produce the same effect. 



A curious instance of this kind has been noted recently by 

 Miyoshi. He cultivated certain fungi in gelatin containing a 

 small proportion of sugar. Under the stratum in which the 

 hyphae were ramifying he placed another containing a larger 

 proportion of sugar, and between the two arranged a membrane. 

 The hj'phae very soon grew towards the stronger sugar solution, 

 and to reach it penetrated the membrane. 



Other instances of similar behaviour might be quoted. To 

 this form of sensitiveness the name of Cliemiotaxis has been 

 given. 



CHAPTER XVI. 



THE NERVOUS MECHANISM OF PLANTS. 



It is difficult to refrain from coming to the conclusion, from a 

 consideration of the facts examined above, that the nervous 

 system of the animal kingdom is represented in the vegetable 

 one. That plants are sensitive to variations in the conditions 

 surrounding them, and that the responses they make to such 

 variations are purposeful, and conduce to the wellbeing of the 



