EXPERIMENT STATION BULLETINS. 277 



cial cultures, and thus actually demonstrate a genetic relationship. To 

 accomplish this demonstration was one of the objects of the present 

 investigation. 



THE CULTURES AND ARTIFICIAL INFECTIONS. 



Artificial cultures of the conldia were repeatedly made during the 

 autumn and winter. The spores germinated more readily in a decoction 

 of strawberry leaves than in any other of half a dozen fluids used, and 

 begun to develop in aboiit six hours from the time of sowing. The general 

 result of the artificial cultures in the autumn was the production of a 

 mycelium bearing certain spherical sac-like bodies of highly organized 

 structure. The winter sowings produced mycelium and outgrowths of an 

 entirely different character, and failed to develop the sac-like bodies of the 

 autumn cultures. Both of these are subjects which Miss Snow hopes to 

 further investigate, and no conclusions concerning them will now be 

 published. 



The sowings of conidia in the spring, obtained from the basidia on the 

 old leaves, produced for the first time mycelium and conidia, like those 

 from which they were derived; but none of the growths obtained in the 

 autumn or winter appeared on the mycelium grown in the spring. 



Numerous infections were made in April and May, by placing both 

 germinated and ungerminated conidia on the upper and the under surface 

 of young strawberry leaves, which w^e believed to be previously uncontam- 

 inated by the fungus. It was found that the germ-tubes bored their way 

 between epidermal cells of the upper surface, but they were not observed 

 to enter by the stomates of the under surface, although infections took 

 place readily from that surface. Entrance by the stomates was certainly 

 not the. usual mode of attack. In about ten days spots, brownish instead 

 of red, appeared on the leaf, and in fourteen days all the places infected 

 usually showed well-defined spots from which conidia were growing. In 

 some cases one leaflet only, in other cases two were infected, and the dis- 

 ease always appeared only on the leaflets and in the places infected; 

 excepting in a few cases where from our control plants, or by other tests 

 we ascertained our plants to be already contaminated. 



The perithecia were diligently sought for, as it was evident that any 

 proof to be obtained in the spring, of their connection with the conidal 

 stage must lie in the artificial cultures of the ascospores. They were 

 found with mature asci in April; and on placing an ascus in a hanging- 

 drop, the spores were observed to germinate in about six hours, within the 

 ascus. The germ-tube developed from one end of the spore, passing, in 

 case of four of the spores, to one end of the ascus, perforating it, while 

 the germ-tubes from the remaining four perforated the opposite end. The 

 mycelium formed by these germ-tubes was larger than that from the con- 

 idia, grew more vigorously, soon producing at the surface of the culture- 

 drop, conidia like those already described and figured as the summer 

 conidia. 



Asci within the perithecium were now examined and the spores were 

 found to be germinating, not only within the asci, but while the asci were 

 in the perithecium, and the mycelial filaments thus produced were crowding 

 out through the ostiolum. 



The interesting discovery of the production of conidia directly from the 

 ascosporic mycelium, immediately suggested the idea that the ascospore did 



