402 THE MICROSCOPE. 



be aware how very minute and yet how systematically formed they 

 are. Preparations of a dozen different species, taken from the grape, 

 potato, parsnip, bean, cucumber, cineraria, veronica, &c., many of which 

 have been in fluid for more than a year, retain their form as perfectly 

 as if only taken from the plant a day. No two are alike in form ; but 

 all are alike in this under the very high powers of the microscope, they 

 show an external hyaline case, with a second utricle, or inner case, full 

 of minute spores. 



If a few leaves of the infected haulm of the potato are taken and 

 gently shaken over a piece of black paper, a quantity of very fine white 

 powder is obtained : place a little of this in fluid, under a power of 

 500 linear ; every atom of this powder will resolve itself into a distinct 

 cell, somewhat of the form of an ace of spades, varying more or less 

 in size from about 3-5000ths of an inch in length. There will be seen 

 a well-defined outline of an inner cell, in which are many hundred 

 greenish-looking spores ; some of the cells will burst, and by using a 

 still higher power it will be seen that these have all the shape and cha- 

 racteristics of the parent cell. Several of them lie easily between the 

 lines on a micrometer, which lines are just 1 -5000th of an inch apart. 

 In Plate XV. the destructive effects upon the tuber are shown. 



There can scarcely be one spot of earth on which these fungi 

 do not fall in their thousands. Insoluble in nature, they wait where 

 they fall the growth of the particular plant for which each has its own 

 affinity, that if that plant grows on that spot, its enemy is near, on 

 the very soil from which it is to draw life. But I further believe that 

 there must be some peculiar disposition yet to be developed in the 

 plant before the fungus will act upon it, to its own rapid development, 

 and the destruction of the said plant." 



Fig. 189, 4 and 6, represents forms of fungi taken in London by 

 the author during the cholera visitation, September 1854. 



Our limited knowledge of the matter does not forbid the suppo- 

 sition that there may be some, even among the purely vegetable fungi, 

 which might, in certain conditions of the human body, when taken into 

 the frame, produce immediate severe constitutional disturbance. The 

 Sarcina may be cited as an instance of this fact. It strikes us, however, 

 as far more probable, that from drains and cesspools reservoirs as 

 they are for excrementitious animal matter may emanate certain spe- 

 cific fungi, the spores of which, under certain conditions of atmosphere, 

 would be given out in such quantities, and in such minute particles, as 

 easily to be carried about by every current of air. Persons in health may 

 inhale and swallow these spores, and escape injury from them. Other 



