ANNUAL ADDRESS. O 



one-third of a ton (750 pounds) would be a fair estimate of the 

 yearly consumption of this vegetable by a healthy, hard-working 

 adult, and I suppose that such a quantity would yield about 170 

 pounds of starch. The arrangement of the starch-cells in the 

 potato is, as I have before said, not difficult to find, and in this 

 part of the country thin sections of some of the tubers would 

 reveal the potato fungus — -Perotiospora infestans. Of this we have 

 had two interesting professional mounts this year in the Society's 

 boxes, showing the resting spores, which appear to be the real 

 source of the mischief, and the fungus itself could also be 

 observed projecting from the stigmata of the leaves. 



In examining different kinds of meal with the intention of 

 referring to them in this paper, I found that the chief distinction 

 was in the size of the starch-cells ; this was marked in some 

 cases by the fact that starches from different sources were 

 contained in the same specimen, mixed in grinding or in 

 conveyance. Identification of the starch-cells in any given 

 sample, is, I believe, generally managed by comparison with 

 standard slides. The same remarks apply to some of the 

 condiments, in which the presence of foreign matters is to be 

 detected by an eye accustomed to see the genuine article over and 

 over again. Mustard, as is well known, is a mixture, and contains 

 the pounded tissues of several plants, which, when so mixed, 

 are by no means easy to distinguish and identify. 



Common Salt, when crystallised on a slide, makes a pretty 

 object, but one not easy to keep in its pristine beauty. Sugar, 

 on the other hand, mounts well, and forms a very fine object for 

 the polariscope ; one was lately circulated in our boxes. From 

 sugar our thoughts naturally pass to preserves, and here the 

 microscopist will find much that is interesting, and perhaps also 

 instructive, if he buys a sample of preserves and examines it 

 carefully ; that is, supposing he is well acquainted with the minute 

 anatomy of turnips and other inexpensive roots. 



In speaking of textile fabrics, I must again mention the 

 comparative method, and for this purpose reference slides of pure 

 materials should be prepared. For a standard slide of cotton 

 place a few fibres of cotton-wool on a glass slip, and cover with a 

 little fluid balsam. A standard slide of silk may be made of an 



