106 REPORT OF THE DEPARTMENT OF BOTANY OF THE 
RELATION ‘OR THE MITE TO” LH EAUIN Gdvisees 
‘ 
The relation of the mite to the fungus is not entirely clear. From 
the inoculation experiments which have been made it appears that 
the fungus rather than the mite is the active agent in producing the 
disease. Bud-rot has been produced repeatedly by artificial inocula- 
tion with pure cultures of the fungus; whereas, attempts to produce 
the disease by inoculation with mites alone have failed. Moreover, 
in the cases of bud-rot produced by inoculation with pure cultures 
of the Sporotrichum no mites have ever been found in the decayed 
tissue. @ Thus, it is plain that the mite is not absolutely necessary to 
the production of the disease. Neither can the association of the 
mite with the fungus be satisfactorily accounted for on the ground 
that Pediculopsis graminum is an abundant species infesting decay- 
ing carnation tissue generally, for such is not the case. In our 
studies the mite has never been observed alone, but always in asso- 
ciation with the fungus. Whether the fungus is always accom- 
panied by mites can not be so definitely stated. In a few cases, 
particularly on June grass, the mites have been absent, apparently, 
but it is possible that more careful search would have revealed their 
presence. 
This almost constant association of the mite and the fungus leads 
to the inevitable conclusion that one must be in some way dependent 
upon the other. Regarding this there seem to be but two hypotheses 
which harmonize at all with the known facts: (1) That the mite 
feeds upon the Sporotrichum; (2) that the fungus depends on the 
mite to carry it from bud to bud. 
We have been unable to obtain any positive evidence that the 
mites feed on the Sporotrichum. ‘The chief reason for suspecting 
that such might be the case is the fact that Forbes*® has observed 
mites feeding upon another species of the same genus, viz., Sporo- 
trichum globuliferum. Webster.“ also, records the occurrence of 
mites (Tyroglyphus siro) in artificial cultures of Sporotrichum 
globuliferum, but thinks they were attracted by the corn meal batter 
on which the Sporotrichum was growing. Sometimes mites make 
*” By F. C. Stewart and H. E. Hodgkiss. 
* Forbes, S. A. Ills. Sta. Bul. 38: 32; same on p. 94 of second reference 
given in footnote No. 4. 
“Webster, F. M. The common cheese mite. Tyroglyphus siro, living in 
Sporotrichum globuliferum. Ann. Rpt. Ent. Soc. Ontario 32: 73. 1902. 
