1893.] PUBLIC DOCUMENT -No. 33. 219 



any nutrient substratum is accompanied by a remarkable 

 formation of the octahedral crystals of oxalate of Imie, 

 which are produced in immense numbers in the mterstices 



between the threads. 



Ascospores sown on sterilized bread saturated with an m- 

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

 beautiful mycelium over the whole surface of the bi-ead and 

 far above it. The ])ranches in many places reached the 

 inner surfece of the tubes, and there developed great num- 

 bers of attachment organs. No spore formation ever oc- 

 curred ; but 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 ot matted 

 threads ; and the foUowing day they had become nearly 

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

 the spores, the cultures contained many larger and structu- 

 rally mature sclerotia. In this case the sclerotia were pi-o- 

 duced wholly upon the surface, and did not rephice at all the 

 substance of the bread, as in a previously descril)ed mstance. 

 Subsequent examination showed that no further development 

 occurred, the activity of the mycelium ceasmg 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 l)e 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 reaching 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 ditterent 

 Germination proceeds rapidly, attachment organs are formed 

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

 trated by funous-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 

 sowin- of a small drop of prune infusion contaming fresh 

 ascosp^ores upon a large leaf of such a plant, the leaf was a 



