Proceedings of the A. A. A. S. 50*7 



phere was widely different from the present. These various 

 data have been as yet but imperfectly studied ; when they 

 shall have received the attention they merit, we may con- 

 fidently calculate on a large increase in our knowledge of 

 the course of events in ancient America. 



Vegetable Parasites and Evolution. 



Vice President Farlow in Section F. (Biology) discussed 

 " Vegetable Parasites and Evolution." The following is an 

 abstract of his address : 



Botanists, as a rule, have contented themselves with con- 

 sidering the ancestral relations of the higher plants only. 

 Hardly any attempt to elaborate a scheme of development 

 for the whole vegetable kingdom has as yet been made. 

 This is due in part to the fact that the older plants, unlike 

 the older animals, have left almost no fossil records. It is 

 my purpose here not to attempt a complete botanical tree 

 of life, but to inquire into the origin of a single group of 

 plants, vegetable parasites. 



A parasitic plant is one obliged to obtain its organized 

 material from other plants or from animals. Parasites 

 subsisting on dead matter are called saprophytes ; those on 

 living substances tiMie parasites. The mould on bread is a 

 saprophyte ; the potato-rot fungus a true parasite. Except- 

 ing plants like the Indian pine and dodder, most parasites 

 belong to the fungi. 



The parasite is usually destructive to the host on which 

 it lives. As the mould grows, the bread disappears ; the 

 decay of the potato is due to the ravages of the potato-rot 

 fungus. There are several cases, however, in which, for 

 the host and parasite, mutual advantages are claimed. 

 Notably among these are lichens, in which the green cells 

 and fungous filaments are said to be reciprocally beneficial. 

 To this mutual relation has been given the name symbiosis. 

 The benefit derived by the fungus is real ; that for the alga 

 is at best hypothetical, for the green cells seem to grow 

 more luxuriantly when free from the fungus. A second 

 case of so-called symbiosis is the root-fungus, Mycorhiza, 



