536 NEW JERSEY AGEICULTURAL COLLEGE 



Po-nrdery Mildews of the Field and Forest. 



The field and forest encircle the plants that have not been men- 

 tioned elsewhere. Of the grains and grasses there is but one mildew 

 that has yet been recorded, namely, Erysiplie graminis DC. This 

 is frequently inet with upon redtop, bhie grass, oats, barley, wheat, 

 etc.. and should any new host for mildew be found among the grasses, 

 it would most likely l)e infested witli this same species. However, as 

 before stated, the only safe way is to make a microscopic examina- 

 tion of the winter fruit and compare results with the descriptions of 

 the various recorded species. 



In a similar way, there is one species that is particularly fond of 

 the members of the great sunflower family, and is, therefore, the 

 mildew of a large list of our worst weeds. This is the Erysiphe 

 cichoracearum DC, and may be generally seen whitening the foliage 

 of sundry ragweeds, fleabanes, solidagos, asters, ironweeds and cockle- 

 burs. It is also often upon the verbenas of the field and the garden 

 species as well, and the same way with the kinds of phlox, wild and 

 cultivated. This mildew is among the worst, because there are so many 

 wild plants that harbor it just outside of the garden fence, or even in 

 the garden, when the latter is not kept free from weeds. 



Another instance of the last-mentioned fact is in evidence with 

 the mildew of garden peas, namely, Erysiphe Polygoni DC, which 

 has many hosts among the most common of our weeds, as, for example, 

 the various buttercups, meadow-rues, lupins, vetches, certain clovers, 

 geraniums, evening primroses and colum.bines, besides several smart- 

 weeds. It is evidently a hard matter to keep such a species of mildew 

 in subjection. 



There are two species unlike the last-mentioned that chiefly infest 

 the woody plants. Thus the Phyllactinia corylea (Pers.) is at home 

 upon birches, alders, chestnuts, oaks, elms, hawthorns, maple, ash, 

 catalpa, etc., and among vines the waxwork (Celastms). The Micro- 

 scophcera Alni (Wallr.) has a similar wide range of trees and shrubs, 

 and when any of the hosts are introduced to the ornamental grounds 

 the mildew does not leave it untouched. 



The genus TJnciuula has some well-marked species that are very 

 limited in number of their hosts — one is upon maples, another upon 

 basswood only, another upon the horsechestnuts and Inickeyes, one 



