220 AGRICULTURAL EXPERIMENT STATION. [Jan. 



with that described by Marshall Ward* as causing a disease 

 of garden lilies. It appears to be able to live saprophytically 

 upon decaying vegetable substances, and is often found upon 

 them ; but I have never been able to detect any traces of 

 decay in lettuce in a house where the fungus was not 

 abundantly to be found. These facts point to the conclu- 

 sion that this Botnjtis is the cause of the rotting, and not 

 merely an accompaniment of decay due to some other cause. 

 It seems doubtful, however, if the affection can be called a 

 disease in the sense that the fungus is able to attack per- 

 fectly sound, healthy lettuce . under ordinary conditions. I 

 have never seen the decay begin elsewhere than at the lower 

 part of the stem ; and it is possible that some injury or imper- 

 fection at that place is necessary to furnish a point of attack. 



The structure of the fungus is very simple. From the 

 creeping vegetative threads arise the erect, spore-bearing 

 ones, which branch spJiringly toward their tips. The ends 

 of the branches become slightly swollen, and from each is 

 developed a number of short, peg-like projections. Each 

 of these now begins to swell at its tip into a globular body, 

 which increases in size and finally becomes elliptical in form. 

 This is the spore, which, when ripe, falls from its attach- 

 ment. The spores germinate promptly in water or a 

 nutrient solution, by pushing out one or more threads 

 each. These threads, when supplied with nourishment, 

 grow rapidly into a much-branched mycelium. In a few 

 days the erect spore-bearing threads begin again to be 

 formed, as above described. Well-nourished specimens 

 growing in a moist atmosphere may, after the first spore 

 cluster has been formed, put out a new branch from the 

 fertile thread, just below the cluster of spores. This thread 

 then grows to a considerable length and then develops at its 

 tip a new spore cluster ; and this process may be several 

 times repeated. The result of such a course of develop- 

 ment is to produce what appear to be very long, fertile 

 threads, with spore clusters scattered at intervals along them. 



Instead of a spore cluster, a thread may produce, appar- 

 ently only when it comes in contact with some solid su'o- 

 stance, a compact cellular mass, which clings closely to the 



* Annals of BoUny, Vol. II., p. 319. 



