Lecture on the Parasitic Fungi of the British Farm. 385 

 cuted by Mr. Bauer. Its common appearance is seen in Fig. 4, 



Common appearance of Mildew. 



which represents it on the straw a little magnified. Its appear- 

 ance, under a first-rate modern microscope is shown in Fig. 5, 



Epitlermis. 



Straw. 

 Fig. 5. Puccinia Graminis, or Mildew, magnifiad. 



where you perceive that these dusty patches are crowds of 

 club-shaped fungi (spores), the thicker end of each of which 

 is divided into two chambers containing the reproductive sporules. 

 They burst through the e'pidermis, or upper skin, which they 

 lift up, and the sporules, dispersed through the air, have been 

 thought to find entrance by the stomata or j^ores. The ground 

 of this notion is, that the patches of mildew are first seen in 

 small cavities immediately beneath these pores, which, as Pro- 

 fessor Henslow, to whom I am indebted for the specimens 

 now before you, observes, " certainly looks very much as if the 

 sporules entered there." With his usual caution, he remarks, 

 '^ that the fact stands in need of proof," and that hitherto the 

 evidence is more in favour of similar fungi being imbibed by the 

 roots of the plants which they attack." We shall shortly see 

 that some experiments on another fungal jJarasiie of wheat, tend 

 to show that these fungi are developed in a manner little sus- 

 pected even by the most accurate observers. This parasite robs 

 the living plants of their juices, and must not be confounded 

 with a very minute fungus called dipazea, which is peculiar 

 to the joints of the straw; nor, as is more common, with another 

 black fungus, which gives a dingy aspect to whole fields 

 towards harvest, and is often called mildew, but which never 

 attacks a plant till it is previously diseased, and which,, for want 



