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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



find in a few days that a number of moulds, yeasts, and bacteria 

 are growing on its surface. The number and kinds of these will 

 depend on several circumstances, of which the season, tempera- 

 ture, moisture, and locality are important on the one hand, and 

 the composition of the exposed fungus-bed on the other. 



Now these growths are weeds, from spores either wafted in 

 from the air, or carried in by flies, &c, or contained in the bed 

 itself, and the experiment is to be compared to one where a garden- 

 bed of soil is dug over and left to nature, and which would soon be 

 covered by weeds, the seeds of which are carried to it by wind, 

 birds, &c, or were already lying there ready to germinate. If in 

 either case we cover over the bed with a glass roof, we can keep 

 out the air-borne seeds from outside, but those already in the 

 ground will soon supply a crop of weeds. If, however, we go 

 further, and kill all the seeds present in the bed to start with, by 

 so arranging matters that we can heat up the soil with its glass 

 roof on, then we can either keep the bed free from plants or sow 

 any we choose. Now botanists had for some time been in the 

 habit of streaking such a prepared bed with the spores they 

 a\ iflhed to grow, and then, as soon as the little thin streak of 

 fungus-plants appeared, taking a small portion off on the point 

 of a clean needle, and again sowing in a narrow streak, and so 

 on till they got only one kind of fungus on the bed. This pro- 

 cedure was modified in various ways by different observers, and 

 Brefeld as early as 1874 had succeeded in so distributing these 

 spores in gelatine that he lifted up only one spore in a drop 

 of the gelatine, and examined its further growth under the 

 microscope. 



Clearly we may compare these methods of microscopic 

 gardening with the common procedure in ordinary horticulture 

 of sowing seeds in long, thin rows, and hoeing out the over- 

 crowded ones and the weeds, and with the practice of pricking 

 out and transplanting of seedlings. With the fungus spores, 

 however, it is generally a case of dealing with spores and even 

 plants which are quite invisible, except under high powers of 

 the microscope, and it was not till comparatively recent times 

 that methods were so improved that we could select and trans- 

 plant these invisible organisms as we now do. 



I may best describe the principles of the present methods by 

 taking that which I have for several years employed in my own 



