INFECTION-POWERS OF ASCOSPORES IN ERYSIPHACE 205 
pot of H. vulgare and a sa t of H. maritimum were raised to the 
level of the top of the Through this ventilation currents of 
e, a o patch 
groups of eats ripe conidiophores; the one control leaf bore a 
small patch of mycelium with young conidiophores. The plants in 
these on pots were now entirely uncover ed to th 
of the greenhouse. On April 27th the three infected leaves bore 
us f Oidium with p asses of spores; 
young conidiophores. On April 30th most of the control plants 
had become infected. No trace of infection a on any plants 
of H. maritimum during the course of the experiment, 
At the time of this experiment the gre i er smal] one— 
contained the numerous plants of barley, now covered with densely 
powdery patches of Oidiwm, used in the previous experiments. In 
order to ascertain to what extent the conidia were carried about in 
the currents of air, a number of glass slides, smeared over with 
glycerine, were suspended from the roof at a little distance over the 
shelves—both over the shelf on which the Oidium-covered plants 
were, and over that on which other inoculated plants under glass 
rs sto t 
give 
lifting or removal of the glass beaker, were exposed to the risk of 
infection from air- Prigie conidia, 
In Exper. no. 11 ascospores were sown, on April 17th, on plants 
of H, vulgare Sates lo old, of Hordeum secalinum ten days old, 
ee of oats fourteen days old. Three leaves were inoculated in 
pot. Many of the ascospores at the time of sowing had put 
forth short germ-tubes. With nape to the H. vulgare, on April 
22nd two of the inoculated leaves showed minute flecks of myce- 
lium. On April 24th the three inoculated leaves a2 pas edgy 
ten, three, and two vigorous patches of mycelium, which 
several cases had produced tufts of ‘conidiophores with anal 
powdery masses of spores. All the control plan —twe ve in 
es 
ks of mycelium had appeared on the control plants. On 
May 8rd more of the controls were infected, and on May 6th the 
Sess kal spread to nearly all the plants in the pot. No trace 
