18 SALMON: SUPPLEMENTARY 
lonicerae has here passed over from the Lonicera Tatarica to the 
Syringa. 
(5) I have not seen a specimen of the Erysiphe on Aster re- 
ferred by Brannon to ‘“ £. communis.’ If the fungus has been 
correctly determined, it would be a remarkable instance of the 
passing over of the species to an unusual host-plant, as the Ary- 
siphe which occurs so commonly on As¢er in the United States has 
hitherto invariably proved to be £. cichoracearum., ' 
It has long been noticed (cf. Léveillé, Ann. Sci. Nat. III. 15: 
219. 1851), that certain species of the Erysiphaceae, or exam- 
ples of a species on a certain host-plant, only rarely, or (in the 
second case) perhaps never, produce perithecia. In connection 
with this subject Neger (54) asks the question: ‘‘ Von welchen 
Factoren hangt die Conidienbildung, von welchen die Perithecien- 
bildung ab?’ With a view to obtain evidence on the subject, 
Neger kept under observation species of mildew growing on Arte- 
mista vulgaris, Ranunculus, and Epilobium montanum. These were 
first kept at a room-temperature in a damp atmosphere under bell- 
jars, and it was found that under these conditions the formation of 
conidia was extremely luxuriant, but that no formation of perithecia 
took place. Afterwards, in November, the plants were placed in 
a cold greenhouse, in which the temperature and atmospheric con- 
ditions were similar to those occurring in the open at the normal 
time for the production of perithecia. It was then found that no 
perithecia were formed on these plants. Neger remarks also, that 
in nature no production of perithecia takes place, as a rule, on 
those host-plants which have been injured by an excessively heavy 
crop of conidia, and cites Uncinula necator on Vitis, Sphacrotheca 
pannosa on roses, and S. Castagnei on Spiraea as examples. Also, 
it is observed that when the development of conidia is slight, then 
an abundant formation of perithecia occurs, e. g., Microsphaera 
alni on Viburnum Lantana, Phyllactinia corylea and S. Castagnet 
on Comarum palustre. Neger, as a deduction from these facts, 
and from the results of his single series of experiments, believes 
that an answer to the question stated above can be given as follows : 
“Conidienbildung wird befordert durch einen aus frischen, tur- 
gescenten Pflanzentheilen bestehenden Nahrboden. Temperatur- 
und Feuchtigkeitsverhaltnisse scheinen von untergeordneter Bedeu- 
