8 
H. C. Experiment Station 
Etiology 
Clover stem rot is caused by a discomycetous fungus, Sclerotinia tri- 
foliorum Erik. This organism is identical with the one which was first 
illustrated by Hoffmann (13) in 1863, but to which he applied the name 
Peziza ciborioides Fries. Furthermore, it is the same as the one which 
is so fully described by Rehm (18) and which he designated as Peziza 
ciborioides Fries. The organism which was originally identified as 
Peziza ciborioides by Fries (9) in his Systema Mycologicum, as has been 
pointed out by Eriksson (6), is entirely different from the clover stem 
rot fungus. In the first place, Fries makes no mention in his description 
of Peziza ciborioides of sclerotia, structures which could not have 
escaped his notice had he been working with the fungus on clover. Then, 
too, he states that the fungus grows early in spring upon stems in moist 
places and heathes, whereas the clover rot fungus appears in Sweden 
during the fall upon the collar of clover plants. Both the time of ap¬ 
pearance and the habitat of the fungi, therefore, fail to accord. It was 
for these reasons that Eriksson regarded Peziza ciborioides Fries as 
applying to a form entirely distinct from the clover stem rot organism. 
Giissow (12) has suggested that the combination Sclerotinia ciborio¬ 
ides Rehm is the most tenable name. In the light of the fact, however, 
that Rehm (18) misidentified Fries’ species there appears to be little 
reason for retaining the specific name ciborioides, when the proper 
generic name Sclerotinia instead of Peziza is employed. 
Morphology of Sclerotinia Trifoliorum 
Although several careful investigations on the morphology of the 
stem rot fungus have been reported, this phase of the problem is given 
attention at this time because of certain statements in recent bulletins 
and text-books bearing on the relationship of Sclerotinia trifoliorum 
and Sclerotinia libertiana. In a bulletin dealing with wilt of alfalfa in 
Hew York, for example, Stewart, French and Wilson (22) state “that 
the fungus causing the disease is supposed to be the Sclerotinia trifolio- 
rum Erik, given in all text-books on plant diseases as the cause of a stem 
rot of clover and which is said to attack also alfalfa. However, Prof. 
R. E. Smith, to whom specimens were sent, reported (20) that “the 
sclerotia were entirely similar to those of Sclerotinia libertiana and 
that they produce a Peziza form which leaves no doubt that the fungus 
really is Sclerotinia libertiana.” Duggar (5) states that some regard the 
clover stem rot fungus as identical with Sclerotinia libertiana. Stevens 
(23) states that they are “by some regarded as identical; sufficient evi¬ 
dence has, however, not been adduced to prove them the same.” More 
recently Smith (21), in an investigation of cottony rot of lemons in 
California, caused by Sclerotinia libertiana, has noted that the same 
