206 THE JOURNAL OF BOTANY 
of sai appeared on any of the plants of H. secalinum or 
fo 
Tn ee no. 12 oe 17th) the same series of inoculations was 
made, On April 22nd the three inoculated leaves of H. vulgare 
bore respectively fifteen, four, and two vigorous patches of my- 
celium; by April 24th the leaves bore sixteen, ten, and five vigorous 
Odum. patches with powdery masses of spores. ‘The control plants 
re all quite free. The glass beakers were at this date removed 
Foie all the poll, On April Oth the three infected leaves bore 
luxuriant powdery Oidium-patches; the controls were still all free. 
On April 30th the fungus had spread to ayaa of the plants in the 
pot. No trace of infection occurred on H. secalinum or on oats. 
In no. 13 (April 18th) three plants of H. vulgare yn 
days old), four plants of H. secalinum (eleven days old), and three 
plants of H. maritimum (twenty-two days old) were inoculated. With 
oe to H. vulgare, infection had frente on two of the inoculated 
leaves by April 24th. On April 27th a two leaves bore patches 
of Oidium with powdery masses of spores. By April 30th the 
fungus had spread ot co eel so weet couttols No infection resulted 
on H. sera 
In Exper. 
three plants in each po ot. With vey to H. hee 00 af the 
inoculated leaves bore, on May 6th, numerous flecks of mycelium 
with young conidiophores; all the control plants were quite free. 
On May 8th the two leaves bore serait powdery Oidiwm-patches. 
On May 14th the Oidium-patches were powdery with masses of 
spores; the controls were still quite Hes. On May 16th the fungus 
h n to spread to the controls. No trace of infection ap- 
peared on any of the plants of H. jubatwm or H. bulbosum. 
Exper. no. 15 (April 30th) three plants each of seedlings 
fseven cae old) of H. secalinwm and H. vulgare were inoculated. On 
May 6th the three inoculated leaves of H. vulgare bore sar rage tt 
fourteen, ten, and three flecks of mycelium, most of which bore 
groups of young conidiophores; the control plants aie) were all 
quite free. On May 8th all the inoculated leaves bore numerous 
and vigorous Oidium-patches with powdery masses of spores; the 
controls were still all free. On May 11th a fleck of mycelium was 
observed on one control plant ; by May 16th the fungus had _ 
to most of the plants in the pot. No trace of infection appeared 
on any * -” plants of H. secalinum. 
r. No. 16 (May 7th) three plants each of H. Zeocriton, 
H. eifur x H. bulbosum (nine days old), and H. vulgare (four- 
teen days old) were inoculated. On May 14th flecks of mycelium, 
some with groups of young conidiophores, were visible on the in- 
oculated leaves of H. Zeocriton _—_ leaves), er trifurcatum (two 
oe and H. vulgare (three leaves). On May 16th these infected 
leaves of the three re Oidium patches with powdery masses 
— all the controls in each pot were free. On May 18th the 
six inoculated leaves in the pots of H. Zeocriton and H. vulgare bore 
numerous patches of Oidiwm with powdery masses of spores; the 
