783 



the attention of Professors in Colleges, equally with Masters in Schools. 

 " Terminology, which is superabundant, containing much that is use- 

 less, must be used with discrimination." And, " We should not teach 

 this or that natural system, since all are more or less incomplete [ra- 

 ther, more or less arbitrary and unnatural], and the student will al- 

 ready have become aware of the existence of natural families from 

 the course of instruction." Our self-deluded system-coiners, who 

 mistake words for things, terms for knowledge, will very little relish 

 such advice.] 



C. 



Extracts from the l Proceedings of the Linnean Society of London.'' 



On the Injuries sustained by certain Plants from the attacks of 

 parasitic Fungi, with particular reference to the Cause of the 

 Potato Disease, by F. J. Graham, F.L.S. 



In order to demonstrate the subject more clearly, Mr. Graham ex- 

 hibited drawings, with magnified figures of several species of para- 

 sites ; and a great many specimens of different plants, both native 

 and exotic, presenting an healthy appearance on those parts which 

 were still free from the attacks of the different species of mildew to 

 which they were subject, but at the same time showing the most in- 

 disputable signs of disease on those parts which were infested by tufts 

 of mildew. The manner in which one plant in particular, Shepherd's 

 Purse {Thlaspi Bursa Pastoris, L.), was effected, was very remarkable. 

 Portions of the stems of this were covered, to the extent of two or 

 three inches, with Botrytis parasitica, which caused them to become 

 gouty or swollen to three times their natural size ; and eventually 

 these parts assumed a brown colour, and a moist putrescent character, 

 which could be traced down the stalks, and in many cases killed the 

 plants. Transverse sections of these blotches, compared with similar 

 sections of a blotch on the potato stalk, exhibited the same effects, 

 the dark fluid having penetrated the tissues of both to a considerable 

 extent. Of all the species of parasitic mildews which he has noticed, 

 Mr. Graham considers those belonging to the genus Botrytis to pro- 

 duce the severest injuries ; and it is an undisputed fact that the potato 

 crops have been universally attacked, during the last three seasons, 

 by Botrytis infestans. 



