oct.is, 1915 Parasitism of Comandra umbellata 135 



beds without the host plants present, little or no growth on the part 

 of the plants of Comandra spp. has taken place, and the plants eventually 

 died. Successful results in growing these species have been accom- 

 plished by only two methods: First, by transplanting sods containing 

 the plants of Comandra spp. from out of doors to the greenhouse with- 

 out breaking the attachments of the roots of the parasite to those of 

 the host; second, by planting seed in flats in the fall out of doors and 

 germinating them in the presence of the roots of host plants after ex- 

 posing the seeds to freezing temperatures by allowing the flats to remain 

 out of doors all winter. 



Dr. E. P. Meinecke, of the Office of Forest Pathology, reports by letter 

 that he has three plants of C. umbellata raised from seed sown in 1913, 

 which remained dormant till 1915, when they germinated and grew 

 without any host plant. These plants were 5 inches high on July 17, 

 1915. This is positive proof that this species of Comandra can live 

 without parasitism if necessary. It remains to be seen whether these 

 plants will continue to grow indefinitely without the presence of host 

 plants. 



The results from our experiments indicate that when the rootstocks 

 of plants of Comandra spp. are broken entirely loose from their root 

 attachment to host plants they usually die through an inability to re- 

 attach themselves. These new data on a subject which apparently has 

 not been previously investigated indicate a greater degree of parasitism 

 in species of Comandra than has hitherto been suspected, and will render 

 more obvious the desirability of the destruction of plants of Comandra 

 spp. in the vicinity of forest-tree nurseries. 



