PEAR MILDEW. 41 



The shape of the spores is, within certain limits, pretty constant, 

 whether it grows on the Pear or Apple ; while those of the plant ou 

 Pyracantha are of a totally different form, and smaller. As the 

 patches, when they occur on fruit, especially on Apples, are more 

 neatly defined than when they grow on leaves, and the remains 

 of the white cuticle are very manifest surrounding the smutty 

 spores, they have given rise to a distinct genus (Spilocaa), 

 in accordance with that superabundance of useless divisions 

 with which Mycology, more perhaps than any other branch 

 of Botany, abounds. Such productions, though far from uncommon 

 amongst Pears, are far more abundant on Apples, insomuch that 

 the produce of whole orchards is frequently almost valueless. 

 The disease sometimes commences in a very aggravated form 

 when the fruit is no larger than a pea, rendering the whole crop 

 abortive. Such was the case this year in one garden with a 

 young and apparently healthy Downton Nonpareil. The New- 

 town Pippins, which are transmitted to the southern states, are 

 often disfigured by it, and though, perhaps, those which are 

 exported to this country are more carefully selected, they are by 

 no means free. The species, however, by which they are affected 

 is not always the same. At least, Spilocaa fructigena, Schwein, 

 of which I have authentic specimens, is not the same species 

 with that before me. 



As regards any remedial measures, I have little or nothing 

 to offer. Such affections are often dependent on causes over 

 which we have no control whatever, and are part of the curse which 

 aggravates all human labour. The best cultivation will some- 

 times fail where atmospheric agency is principally concerned, and 

 in the present case, where everything has been done to secure a 

 proper condition of soil and a due exposure of the leaves to light 

 and air, immense injury has been produced year after year with 

 every variety of season and treatment. A figure of the little 



parasite is subjoined. 



