6 
COLTUBB OF 9ILKWOBM8. 
appeared to eat it the same if it had been good leaf. Tlic 
Cliineso said tliat tlie worms were quite healthy and that deatha 
amoii<,'gt tliem were very rare, but subsequeiit events showed 
that this information was ineorrect. Thev adiiiitted that in con- 
setjuence of the disease they had l^een short of leaf, and had not 
been able to rear as many worms as they expected. 
A micros eopical examination of sections of the leaf showed 
that the disease was caused by a f-unj^ms f^rowin^^ entirely with- 
in its suhstanee. A spore evidently settles on the imder-side of 
a leaf, throws out a thread which j)enetratea into the fii^st 
stonmta it eomes to, and then, findmg nonrishment, increases 
within the tissues of the leaf, which becomes yellow and con- 
sidembly swollen at the centre of the spot. One or more of the 
stomata on this swelling become much enlarged internally, and 
filled wnth brij^ht yellow spores^ wliieh eventually are forced by 
those beneath them out of the now expanded external orifice of 
the stomata. 
The spores are rather iiTegukr in form, some being spheri- 
cal and others oval They measure about ^,y,-^jinch in diameter. 
In water the transparent spore case becomes distended and 
separated from the granular yellow nucleus, which it then 
encloses, as the white of an egg does the yolk. When plac*>d in 
a drop of water on a cover-glase, inverted over an open vasilined 
cell of a microscope slide, so that evaporation is prevented, the 
spores may be seen to swell as above stated and eventually to 
burst ; the yellow contents then float out as separate grauvdes, 
which each l>egin to swylJ until they attain nearly the size of the 
original com2x>und spore, and in aVjout four hours the swcillen 
granules, which are spherical and are the true spores, Iwgiu to 
throw out slender, distantly jointed, waved threads, sometimes 
branched. Occasionally one or two of the yellow granules swell 
within a mother cell and germinate, and the mycelial thread or 
threads pierce the wall of the mother cell, which then'^hus the 
appearance of being an actual spore ; but I lieheve I am right in 
saying that it is not so in reality. I have not l)een able to con- 
tinuously watch forhours a iJarticidar cell under the microscope, 
as should be done in investigations of tliia sort, Imt have only 
been ai>le to devote spare minutes at odd times to the work, 
therefore it m just posidble that I have misinterpreted the 
method of germination. It is nearly certain that the sjiores only 
germinate when in a drop of water, and attack the leaf only, 
when that drop happens to be on the tmder-side of a leaf. 
The mulberry which has beeu planted at Ayer Kuning w-as 
introduced from Chiua. The Chinese, however, say that they 
have no recollection of having seen the leaf disease on the 
