116 VEGETABLE PAEASITES. 



employing parasiticidal means, and strengthening and improving 

 the system. 



Physiology of vegetable parasites. They all show 



1. Nutrition. Assimilation may be recognised distinctly, or 

 only indistinctly or not at all.. The products of secretion are 

 none or very sparing. Sometimes a few drops of oil are found 

 on the surface or underneath the spores, and even these may be 

 viewed as the product of the transformation of the amylaceous or 

 nitrogenous matter in plants. 



2. Development.- This varies according to the species, it is, 

 however, generally speaking, very rapid everywhere with vegeta- 

 ble parasites, in consequence of the predominant assimilation. 



3. Reproduction. This function is likewise very intense and 

 rapid. The spores spring up rapidly in masses, and are capable of a 

 very easy dispersion either by currents of air carrying the spores, 

 or by water in which they are frequently whirling about. 



Effect of the parasite on its host. The spore of the parasite 

 germinates as soon as it has settled down on some part of the 

 body, or it penetrates first deeper into the body underneath the 

 epidermis, or in the open cavities of the body. The spores pene- 

 trate rarely deep at first, but almost all will do so as soon as the 

 filaments of the mycelium are formed, which penetrate rapidly the 

 surface of the membranes and tissues, disturbing the functions of 

 these parts, and killing smaller animals sometimes in two or 

 three days ; as, for instance, the eggs of reptiles and fish (as 

 those who endeavour to rear fish artificially have to their cost 

 experienced), or the Batrachia themselves, upon whose skin they 

 frequently settle down. The penetrating of the filaments is 

 sometimes merely mechanical into readily formed cavities of the 

 body, as in the follicles of the hair; sometimes it is caused by the 

 elevation of the epithelium. It is, however, soon followed by 

 organic action, since the hard and specifically heavier spore 

 presses upon the soft tissue underneath and causes resorption in 

 such places. The same occurs when the action of the organ on 

 the spot where it lies presses it in deeper, or when its constantly 

 increasing size causes molecule after molecule to be subjected to 

 resorption underneath its weight. It may at the same time be 

 observed that the process of germination, which goes on everywhere 

 in nature with an unmeasurable display of power a process by 

 which the hard husk of the vegetable seed (spores) is rent, and 

 the young plant enabled to push aside the soil, to lift and to break 



