54 MICROSCOPIC FUNGI. 



them amongst a host of others ; subject, as they 

 may be, to slight deviations in form, resulting 

 either from external pressure, checks in develop- 

 ment, or other accidental circumstances, or the 

 variations of age. 



There is no doubt in the minds of agriculturists, 

 botanists, savans, or farm-labourers, that the mil- 

 dew is very injurious to the corn crop. Different 

 opinions may exist as to how the plants become 

 inoculated, or how infection may be prevented or 

 cured. Some have professed to believe that the 

 spores, such as we have seen produced in clusters 

 on wheat straw, enter by the stomata, or pores, of 

 the growing plant, " and at the bottom of the hol- 

 lows to which they lead they germinate and push 

 their minute roots into the cellular texture." Such 

 an explanation, however plausible at first sights 

 fails on examination, from the fact that the spores 

 are too large to find ingress by such minute open- 

 ings. It is improbable that the spores enter the 

 growing plant at all. The granular contents of 

 the spores may effect an entrance either through 

 the roots or by the stomata, or the globose bodies 

 produced upon the germination of the spores may 

 be the primary cause of infection. We are not 

 aware that this, question has been satisfactorily 

 determined. It is worthy of remembrance by all 

 persons interested in the growth of corn, that the 

 mildew is most common upon plants growing on 

 the site of an old dunghill, or on very rich soil. 



