164 Professor G. V. Poore [April 24, 



tlie housewife, the furrier, and the keepers of museums. These 

 animals gnaw the softer parts, such as ligaments, and leave nothing 

 but a jfine powder behind them, which is in fact their dung. 



The last and eighth squadron consists solely of beetles, which 

 clean up the debris, in the shape of dung, shells, pupa cases, &c., of 

 the seven squadrons which have preceded them. 



M. Megnin, being an entomologist and not a bacteriologist, deals 

 exclusively with the insects concerned in making away with a carcase, 

 but it is evident that bacteria work hand in hand with them. 



There are many other instances which may be quoted of the co- 

 operation of fungi with other organisms, and it is only of late years 

 that we have appreciated the fact of symbiosis or the living together 

 of two organisms for the mutual benefit of each. This fact was first 

 pointed out in so-called lichens, which are now shown to be comjjles 

 bodies consisting of a fungus and an alga, living in symbiotic com- 

 munity for the mutual benefit of each. 



It was next shown that the Papilionaceous Leguminos^ are imable 

 to flourish without certain bacterial nodules which grow uj)on their 

 roots, and by the instrumentality of which they can appropriate the 

 nitrogen of the air, and thus the fact, familiar for centuries, that 

 the leguminosae leave the ground in a state of great fertility, while 

 they are singularly independent of nitrogenous manures, has been 

 explained. 



But if the plants themselves are independent of dung, it is not so, 

 apparently, with the symbiotic nodules, which seem to flourish far 

 more vigorously in rich garden ground than they do in comparatively 

 poor farm land. Thus Sir John Lawes has grown clover in a rich 

 old garden for forty-two years, and has had luxuriant crops every 

 year. 



According to my own observation on the scarlet runner bean these 

 nodules are more plentiful upon the roots which grow superficially 

 than upon those which run deeply. 



Symbiosis is observable in many plants other than leguminos88, 

 and it is certain that many of our big forest trees depend for their 

 nourishment upon fungi which grow upon their roots. 



By the kindness of my colleague. Professor F. \V. Oliver, I am 

 able to show you upon the screen the so-called Mycorhiza as it grows 

 upon the rootlets of the beech. 



In the upper left-hand corner is a portion of root showing its 

 characteristic fungoid covering (natural size). To the right is a por- 

 tion enlarged — the thinner strands behind, being parts of the fungus 

 in the soil without an axis of root. Below is a root apex with fungal 

 sheath enlarged. 



The next slide is from a drawing, by Professor Oliver, of Sarcodes 

 Sanguinea, the Californian snow plant, a remarkable saprophyte which 

 is destitute of chlorophyll. 



The drawing shows the fungal sheath, and, to the right, the 

 epidermis and one cortical layer of the root. The black scales in the 



