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THE POPULAR SCIENCE MONTHLY 



A small tuft was then carefully taken from the apple, and placed on 

 a glass slide, and its area measured with the micrometer, and the num- 

 ber of fruit-stalks it contained determined. The surface was y^ of 

 an inch square, and the number of stalks 800. As the square inch is 

 a familiar unit of measurement, the estimate made for that small ex- 

 tent of surface gives 3,200,000,000 spores. It is a well-known fact 

 that not only inches, but feet, and even acres of this mould are pro- 

 duced, and the number of spores for daily use must be perfectly appall- 

 ing. They are light, airy, and invisible to the naked eye aud therefore 

 ecape our notice; were they female mosquitoes, we would realize their 

 nearness and number. With such multitudes of germs produced we 

 need not wonder that the sowing for moulds should be natural and 

 complete. The light which the microscope throws upon this subject 

 makes it unnecessary to resort to " spontaneous generation " to ac- 

 count for the almost certain growth of mould when the proper condi- 

 tions are combined. 



Fig. 9. Peziza Fucheliana. De Bary. 



When a slice of bread which has been thoroughly overrun by the 

 Penicillium is left under the bell-jar, another mould almost invariably 

 comes, covering the blue surface with a rose-colored coat. The 

 asexual spores and their method of formation are given in Fig. 8. 

 It will be observed that the fruit-stalks are unbranched, the spores 

 when mature always double, and arranged on the stalks in whorls. 

 The development is from below upward : a showing an old stalk with 

 the youngest spores nearly ripe, and some of the older ones gone from 

 their attachments ; at b is a younger stalk, where the older whorls 

 are complete and the upper ones small and indistinguishable; c is a 

 more enlarged view of a cluster of ripe spores. After this mould, 

 which is of slow growth, has run its course, the bread seldom produces 

 any other forms, and for further study a new culture must be made. 



