578 



Black-Spot. This is due to a fungus (Phyllachora trifolii) 

 which attacks the leaves of clover causing dead spots and dark dis- 

 colorations on the under side of the leaves. As a rule these attacks 

 come so late in the working life of the leaves that the injury is slight. 



Leaf -Spot. A leaf -spot of white clover referable to an anthrac- 

 nose fungus (Ascoehyta) has been described from our region al- 

 though not definitely determined in Ohio. The injury which may 

 result cannot be now stated. 



Rust. The various sorts of the cultivated clover, Red, Alsike, 

 Mammoth, etc., are attacked by a clover rust (Uromyces Trifolii). 

 If one will examine the small, dark spots in the clover leaves he will 

 find a cluster of this reddish fungus beneath. This rust does not 

 spread to other plants than clovers and is commonly regarded as 

 more disfiguring than destructive. It is not nearly so injurious as 

 the leaf-spot of alfalfa which is similar in appearance. 



Root Nodules and Root Tubercles Upon Leguminosae. Upon 

 removal of the roots of the clover plant from the soil one finds minute 

 enlargements which are the subject of frequent inquiry. These are 

 nodules or tubercles as they were formerly called, caused by the 

 messmate-living of certain nitrifying organisms, or microbes, with 

 the clover plant. To these microbes in this communal life is due 

 the power of withdrawing nitrogen from the atmosphere and fixing 

 it in the tissues of the clover plants. The same applies in general 

 to the nodules upon plants of this order, the Papilionaceae. It thus 

 follows that these nodules are the normal condition of properly 

 nourished leguminous plants of the order Papilionaceae, and it like- 

 wise follows that the full value of this work of nitrogen fixing is 

 only realized for manurial purposes when the tissues of the clover 

 plants decay in the soil. 



Clover Dodder (Cuscuta epithymum}. Clover dodder is an 

 old enemy and is well known throughout the country. Judging by 

 its prevalence on clover during the summer of 1907, it seems prob- 

 able that its nature is not thoroughly understood by the farmers. 

 The disease was very common in all parts of the state where red or 

 alsike clover was grown, and was much more abundant than it has 

 been in previous years. 



Dodder on Clover. The dodder of clover is recognized at a dis- 

 tance by the yellow appearance in spots of the clover fields. At 

 close range, it will be seen to consist of branching yellow threads 

 which twine about the stems and leaves of the plant. At first the 

 dodder will be seen only in a small area, infecting one or two plants. 

 It rapidly spreads in all directions by branching of the threads from 

 these to other plants till large areas are covered. During this spread- 

 ing, the plant first infested will gradually be killed by the parasite. 

 The dodder dies with it, but continues to grow along the edges of 

 the spot, so that, in the late season, dead spots surrounded by a circle 

 of dodder-infested plants may be observed in clover fields. The 

 dodder in the meantime has blossomed profusely and ripened its 

 seed. 



