508 Canadian Record of Science. 



and the trees on which it grows. Frank, who discovered 

 the Mycorhiza, supposed that the fungus conducted all the 

 food from the soil into the roots. However this may be, 

 Hartig has shown that the fungus is not necessary to 

 the tree, and Kamienski claims that it is really harmful. 

 Both lichens and Mycorhiza must be considered cases of true 

 parasitism, not symbiosis. The animals and unicellular 

 algas offer more promising examples of symbiosis, for here 

 the products of assimilation are such as to render a condi- 

 tion of mutual benefit readily conceivable. Botanists seem 

 to have over-estimated the number of cases of symbiosis, 

 and to have included among them cases of true parasitism. 



It is highly probable that vegetable parasites originated 

 at an early epoch from non-parasitic forms. There is rea- 

 son for believing that the earliest forms of undoubted plants 

 were unicellular and not unlike Protococcus. These once 

 having established themselves, there is no reason why they 

 should not have been quickly followed by colorless, unicel- 

 lular parasites like Chytridium. The transition from Pro- 

 tococcus to Chytridium is easily effected. As soon as a 

 Protococcus has developed the power of attaching itself to 

 other protococci, lost its chlorophyl and developed moans 

 of penetrating the wall of its host, it has assumed all the 

 essentials of a Chytridium. Whether the filamentous and 

 higher parasites have been derived from such chytridiaceous 

 forms is not easy to say. It is, however, perfectly possible. 



It seems not unreasonable to suppose that true parasites 

 may have originated at a very remote period from iiod- 

 parasitic plants ; but may not saprophytes first have devel- 

 oped from non-parasitic plants, and then parisites from 

 saprophytes ? The question is one not to be answered from 

 actual knowledge ; the probabilities seem to favor the view 

 of parasites originating directly from forms like Protococcus. 



Still another possibility must be noted. Could not both 

 parasitic and non-parasitic plants have originated simul- 

 taneously from a protoplasmic ancestor, neither animal nor 

 plant ? The Myxomycetes favor this view. But the Myx- 

 omycetes may be animals and, if plants, they have remained 

 in a*low condition and have no off-shoot representing higher 



