1893.] PUBLIC DOCUMENT — No. 33. 219 



any nutrient substratum is accompanied by a remarkable 

 formation of the octahedral crj'stals of oxalate of lime, 

 which are produced in immense numbers in the interstices 

 between the threads. 



Ascospores sown on sterilized bread saturated with an in- 

 fusion of prunes, in tost tubes, produced an abundant and 

 beautiful mycelium over the whole surface of the bread and 

 far above it. The l)ranches in many phices reached the 

 inner surface of the tubes, and there devek)ped great num- 

 bers of attachment organs. No spore formation ever oc- 

 curred ; })ut a week after the beginning of the culture dense 

 white masses were detected among the looser threads. On 

 examination these proved to. be very firm lumps of matted 

 threads ; and the following day they had become nearly 

 black in color. A day later, nine days from the sowing of 

 the spores, the cultures contained many larger and structu- 

 rally mature sclerotia. In this case the sclerotia were pro- 

 duced wholly upon the surfiice, and did not replace at all the 

 substance of the bread, as in a previously described instance. 

 Subsequent examination showed that no further development 

 occurred, the activity of the mycelium ceasing with the 

 formation of the sclerotia. 



If ascospores be sown in water on the surface of a cu- 

 cumber stem, or at its growing point, it might be expected 

 that the germ tubes would promptly penetrate the tissues 

 and infect the plant, if it be really true that this fungus is 

 the efficient cause of the disease. But, although carefully 

 protected from drying, they utterly fail to attack the plant, 

 even though sown in a fresh cut reachino; to the active tissues 

 of the plant, when sown in water only. On the other hand, 

 if they be sown on a healthy and uninjured part of the plant, 

 in a drop of nutrient fluid, the result is very different. 

 Germination proceeds rapidly, attachment organs are formed 

 on the surface of the plant, and soon this surface is pene- 

 trated by fungus-threads which quickly spread through the 

 tissues. In this way infection takes place, and the plant is 

 lost. Even the leaves of a plant kept in a moist chamber 

 are in this way readily attacked. Three days from the 

 sowing of a small drop of prune infusion containing fresh 

 ascospores upon a large leaf of such a plant, the leaf was a 



