Notes and Brief Articles 



125 



" Lightning injury to Hevea brasiliensis," by Carl D. La Rue. 



Lightning injury to the Para rubber tree (Hevea brasiliensis) rarely manifests 

 itself in tearing or breaking of the trunks or branches. Usually a single small 

 branch at the top of the tree dies first. From this point the death of the 

 branch continues downward until the trunk is reached, then the trunk dies 

 back until the root is reached and finally the whole tree is killed. Several days 

 may elapse from the time the injury is first visible until the whole tree is 

 dead. The progressive death of the tissues is extremely suggestive of invasion 

 of the tree by some destructive organism. The injury has been attributed to 

 Diplodia and the supposedly guilty organism named Diplodia rapax. Cultures 

 by the author showed Diplodia to be the only organism constantly present, but 

 this is now known to be secondary and not the cause of the death of the tree. 

 The injury is most pronounced in the cambium region. Here the tissue be- 

 comes deep-purple in color and decays with great rapidity, making it easy to 

 trace the progress of the injury. The purple coloration is regarded by the 

 a-uthor as diagnostic for this type of injury. Frequently, trees surrounding 

 the dying tree show injury in lesser degree, which develops later than of the 

 tree most seriously injured, thus suggesting the spread of an organism from 

 one tree to the other. 



" A dry rot of the sugar beet caused by Corticium vagum," by B. L. Richards. 



A serious and apparently undescribed rot of the sugar beet has been ob- 

 served during the past season in a number of beet fields in northern Utah and 

 southern Idaho. The disease, as it appears in the field, is confined to some- 

 what definitely delimited areas wherein every beet may become infected. The 

 roots of the diseased beets show circular lesions characterized by very promi- 

 nent alternating light and dark brown concentric rings. The disease is typi- 

 cally a dry rot. In the later stages a deep pocket, partly filled with a dry pulp 

 composed of mycelium and decayed host tissue, results at each point of infec- 

 tion. With numerous points of attack the beet by harvest time may be con- 

 verted into a dry, pithy mass. Numerous isolations from sugar beets, taken 

 from a number of fields, have given what, from cooperative studies, appears to 

 be a single strain of Corticium vagum B. & C. Inoculation shows this strain 

 to be extremely virulent, and lesions have been produced on normal healthy 

 beets with unusual uniformity. 



W. A. MURRILL 



