616 
Journal of Agricultural Research 
Vol.XXXI, No 7 ■ 
tissues in spore-germination studies of Botrytis cinerea , several ex¬ 
periments were devised in order to test similar effects on microconidia. 
To be sure that there were no small bits of mycelium in the spore 
suspension, the microconidia were filtered through filter paper. 
The filtrate, free from mycelium, was then used to inoculate freshly 
cut slices of carrot root and to be sprayed on leaves of head lettuce. 
The inoculated plants were held in moist chambers, at room tem¬ 
perature, in diffused light, and examined daily for symptoms of 
infection. Parallel with these inoculation experiments, several 
hanging-drop cultures were made in van Tieghem cells by adding bits 
of carrot-root tissue to the drops so that growth might be observed 
with the microscope. 
The results of these experiments and others of similar nature were 
disappointing. No infection of the host occurred, and only an 
occasional short germ tube could be found in the hanging-drop 
cultures. Many hanging-drop cultures of microconidia in various 
dilutions of the freshly expressed juices of the host plants listed in a 
previous paragraph were made from time to time. In most of 
these cultures germination either was very feeble or there was none 
whatever. When germination took place, the germ tubes developed 
2 or 3 spore diameters (7 to 12 microns) in length within 48 hours, 
and then stopped growth. Cooked broth or decoctions in general 
gave a higher percentage of germination than fresh juices of the 
same plants, but in none could development be induced when single 
spore cultures were attempted. Consequently, no culture has ever 
been obtained by the writer which can definitely be traced to a single 
germinating microconi dium. 
In addition, sugar solutions of various strengths, as well as the 
standard nutrient salt solution as used by Duggar ( IS ), and Pfeffer’s 
nutrient solution, were used as media. In these, as in previous 
experiments, only a small percentage of the spores produced germ- 
tubes (pi. 4, G). These ceased growing after 48 hours, and no changes 
in light or temperature conditions were found that would induce 
them to further activity. 
The only cultures obtained from microconidia during these studies 
were from plantings made on potato and prune agar plates. Micro¬ 
conidia suspended in sterile distilled water were filtered through 
filter paper, which was found to remove particles of mycelium, and 
drop plantings of the filtrate were then made on hard agar in Petri 
dishes. No growth was visible to the unaided eye for two days, but 
on the third day mycelial development was observed in all plantings. 
Within one week these cultures made a normal growth of mycelium 
and sclerotia which appeared similar in every way to the usual cultures 
of S . libertiana . 
It appears, therefore, that conditions must have been favorable 
in these experiments for the full development of the microconidia, 
although, as far as the writer is aware, these conditions were no dif¬ 
ferent than those under which many other unsuccessful germination 
tests were made. 
In order to test the microconidia for a reaction to oxygen, a series 
of hanging-drop cultures was made in the usual way. A drop of 
distilled water with dioxygen added as a source of oxygen was used 
as a medium. Cultures were made using the following percentages 
