Oct. 1, 1925 
Sclerotinia Species Causing Decay of Vegetables 
609 
spores thus caught on the agar film can be seen with the low power 
of the microscope and marked by a dot of ink on the bottom of the 
Petri dish.* By choosing a thinly seeded portion of the plate for 
marking the spores, and by using reasonable care, a small portion of 
agar above the marked location of the spore can be lifted out without 
fear of getting more than one spore. If, however, the agar is cloudy 
and there is doubt as to the location of the spores, it has been found 
practical to hold the Petri dish culture for 12 hours, or until short 
germ tubes have started. When observations are made early it is 
not difficult to locate single germinating ascospores. 
ASCI AND SPORES 
The spore and ascus measurements are very important in dis¬ 
tinguishing between species of the genus Sclerotinia, and for that 
reason a large number of measurements from numerous cultures have 
been made. The average measurements of typical large sclerotial 
strains of Sclerotinia from important host plants are listed in Table 
IV. For the sake of comparison the corresponding measurements of 
S. minor (18), S. ricini (15 and 16), and S. intermedia (24) are also 
given. This table .shows a striking similarity in spores and asci of 
the 28 strains belonging to the large sclerotial type herein listed. 
While there is a slight variation between strains from different hosts, 
this difference is no greater than that within strains from the same 
host or the variations even within a given strain. The average 
measurements of asci ranged from 8.2 to 10.2 microns in width and 
from 125.4 to 160.4 microns in length, the mean of the averages of 
all large sclerotial strains being 9.2 by 144.3 microns. The spore 
averages ranged from 5.9 to 7.3 microns in width, and from il.7 to 
15.1 microns in length, their mean being 6.6 by 13.3 microns. 
Table IV .—-Average measurements in microns of spores and asci of several strains 
of Sclerotinia libertiana as compared with each other and with S. intermedia, 
S. minor, and S. ricini 
S. LIBERTIANA 
Culture 
No. 
Host 
Asci 
Spores 
822 
Bean_ ... _ __ ... _ __ 
9.5X156.4 
8.2X144.7 
9.2X144.4 
8.6X142.8 
6.7X12.7 
7.0X14.1 
6.7X13.8 
6.6X13.2 
7.0X14.0 
6.8X13.4 
7.3X12.4 
6.8X13.3 
6.9X13.3 
6.0X11.9 
6.9X13.3 
6.6X13.1 
6.6X13.2 
5.9X12.6 
6. 2X12.8 
283 
Carrot..... .... 
763a 
.do... .. 
760 
Cauliflower_____ 
215a 
.do____ 
9.9X155.0 
9.4X146.3 
9.3X143.6 
9. 5X144.1 
9.5X151.3 
187b 
Celery.. ...__ 
695 
_do....... __. 
S/24 
738 
do . 
_do_ ______ 
345 
Chicory_____ 
9. 0X133.0 
749 
Endive_ ___ . _ ____ 
9.8X145.9 
612 
Lemon____ _ 
9.4X144.6 
, 344 
Lettuce___ __ __ 
8.8X130.4 
8.2X138.1 
8. 6X138.3 
693 
_do___ _ ______ _ _ _ 
705 
.do_______ 
415 
_do___......... 
9.1X143.2 
6.4X13. 0 
719 
.do......„. 
9. 2X155. 7 
10. 2X158. 5 
6.8X13.5 
7. 0X14.0 
7.1X13.8 
1466 
.do.... _ -__ 
349 
_do....... 
9.9X150.8 
261 
Parsnip.___..... 
8.7X138.3 
6,8X12.9 
744 
_do__ ____ 
9. 0X136. 9 
9.4X160.4 
6. 5X13.9 
7.0X14.4 
732 
Salsify.... .. 
819 
.do_______ 
8.6X141.8 
6.7X14.0 
6.2X13.2 
6.9X11.7 
6.2X15.1 
6.4X13.0 
820 
.do... _ _ __ 
8.6X125.4 
9. 6X139.8 
9. 3X145.1 
9:0X142. 8 
833 
_do ...._ _ __ _ _ _ __ 
834 
_do_ ___ 
177 
Sweet potato_ _ ___ 
1567 
_do___ __ __ ___ _ _ 
9. 8X152. 7 
0.4X12.0 
