24 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



the plants attacked by fungi, and the germ-tubes leave the out- 

 side of the plant, and penetrate into the tissues in obedience to 

 this cheinotactic influence ; at least, there seems no other 

 explanation of the curious phenomena witnessed, for it is possible 

 to make a fungus which ordinarily is not a parasite enter into a 

 leaf and become parasitic by artificially injecting the leaf with 

 the attractive chemical, and we have reason to believe that in 

 many cases of epidemics the disastrous onslaught of the parasite 

 is in great part due to the fact that the cells of the host-plant 

 are unduly charged at the time with such substances as I have 

 referred to. 



No less remarkable are the discoveries which microscopic 

 gardening has elicited concerning the way the fungus attacks 

 the solid cell-walls of the host-plant. Solvents of various kinds 

 have been shown to be excreted from the tips of the fungus - 

 tubes, which dissolve the cell-walls and enable the tubes to pene- 

 trate and pierce holes through what would otherwise be im- 

 passable barriers ; and if a drop of such solvent be squeezed out, 

 and a piece of solid cell-wall be steeped in it, the latter melts 

 away under our eyes. As Professor Green has shown, similar 

 bodies are produced by pollen-tubes, so that we now see how 

 these pierce their way down the style of the flower. 



Not because I have exhausted the subject, but in fear lest I 

 should exhaust your patience, I am led to bring this sketch of 

 the subject and results of microscopic gardening to a close. I 

 hope sufficient has been made clear to show that gardeners on a 

 large scale — by which I mean horticulturists, farmers, and 

 foresters, as well as all who grow plants — are vitally concerned 

 in the minute operations of microscopic gardening, for not only 

 are investigators bringing to light daily discoveries of the highest 

 importance to science as a whole, but results of the greatest 

 practical importance ; and I am sure you will agree with me 

 that just as these gardeners on a minute scale have learnt, and 

 still have to learn, much from your practice on a large scale, so 

 you will find much of value and interest in their pursuits, which 

 have to be conducted with a rigour and precision worthy of 

 comparison with the most refined and difficult operations of 

 modern culture, and demanding the highest scientific attain- 

 ments. 



