1890.] PUBLIC DOCUMENT — No. 33. 211 



16. Truffles {Tuber acecti) are a small group of subter- 

 ranean saprophytes, some of which are highh' prized as 

 articles of food. 



17. Imperfect fungi is a general term to include an 

 immense number of forms supposed to be mostly early 

 stages in the development of members of some of the groups 

 already described, especially various summer-spore forms of 

 funo:i belonsfino^ to oroups 13, 14 and 15. Here are com- 

 prised the very different forms known under the names 

 Sjphmropsidem, Melanconiecc , Hyj)homycetes, etc. The spores 

 are usually borne naked on the ends or sides of spore- 

 producing threads, and germinate at once, as a rule. These 

 fungi are, in large proportion, parasites, and produce 

 diseases of widely ditiering external appearance, known 

 variously by the names " anthracnose," " blight," " spot," 

 " scab," " rot," etc. 



A fuller account of these fungi is impossible, except by 

 subdividing them into several groups, because of t*he very 

 heterogeneous character of the contents of this general 

 catch-all for forms not placed elsewhere. The fact that such 

 a miscellaneous and enormous collection of ' ' imperfect " 

 form-species must form a part of any enumeration of fungi, 

 is the best evidence of the incompleteness of our knowledge. 

 In proportion as that knowledge increases, the extent of this 

 collection must diminish. 



The above outline covers the principal fungi, and will, it 

 is hoped, to some extent subserve the purposes for which it 

 has been prepared. Being now in possession of some general 

 facts concerning fungi, we may attempt to deduce from them 

 some of those principles which must guide us in attempts to 

 lessen or prevent the ravages 'of diseases caused by these 

 plants. 



Since parasitic fungi develop, for the most part, within 

 the tissues of their hosts, it is evident that there is little 

 possibility of saving a plant once fairly infected ; for what 

 would kill the parasite would ordinarily be fatal to the host. 

 The powdery mildews, being external parasites, may perhaps 

 be killed after they are Avell developed. Our chief aim, 

 however, must be to protect the plant by the thorough 

 application to its exposed surfaces of some preparation which 



