202 NEBRASKA STATE HORTICULTURAL SOCIETY. 



are propagated, and to run in it from one to another, resulting in the 

 rapid destruction of the plants in the bed. Upon taking up the speci- 

 mens, the parts affected are found to be in the early stages of decay, 

 and penetrated throughout, even in the interior of the epidermal ap- 

 pendages, by the branching iilaments of a fungus. 'Damping-off' is due 

 to the action of several parasitic organisms, of which Pythium de hary- 

 anum Hesse, is one of the most common" (Spalding, "The White Pine," 

 Bull. 22, Div. of Forestry). According to Ward ("Timber and Some of 

 its Diseases"), the fungus PliytopMhora omnivora, a common one in 

 European nurseries, may be taken as typical. This is a mildew of the 

 Peronosporaceae, and need not be described further. It is fostered by 

 moisture, warmth, insufficient air, and the presence of decaying organic 

 matter in the soil. "Damping-off" occurs very frequently in the govern- 

 ment nurseries at Halsey, where the loss sometimes amounts to 90 per 

 cent of the seedlings in a bed. This disease attacks especially the 

 smaller seeded pines, such as the .Jack pine and Scotch pine, which start 

 life with a limited food supply, and hence have less energy to resist such 

 atta,ck. The remedial measure most successful at Halsey has been the 

 aeration of the stems of the seedlings, obtained by covering the beds 

 with gravel, which prevents the splashing of mud on to the stems. 



(2) Pine Blister: Pine Cluster-cups. {Goleosporium senecionis Fries: 

 Periderinium pint Wallr. 



This fungus of the family Uredinaceae, one of the heteroecious para- 

 sites, is one of the common enemies of the pines in Europe, and members 

 of the same genus, if not the same species, are described as attacking 

 Jack, red, white and Scotch pines in Minnesota (Spalding). The fol- 

 lowing is furnished by Ward: 



"In the months of April and May, the younger needle-like leaves of 

 the Scotch pine are occasionally seen to have assumed a yellow tinge, 

 and on closer examination this change in color, from green to yellow, 

 is seen to be due to the development of what looks like small orange- 

 colored vesicles or blisters standing off from the surface of the epidermis, 

 and which ha,ve in fact burst through from the interior of the leaf. 

 Betvvreen these orange-yellow blisters the lens shows certain smaller 

 brownish or black specks. Each of the vesicular swellings is an aecidium, 

 and each of the smaller specks is a spermogonium. 



"On the younger branches of the Scotch, "Weymouth and Austrian 

 pines, and some others, there may also be seen in May and June similar 

 but larger bladder-like orange vesicles (aecidia) bursting through the 

 cortex, and here again careful examination shows the darker smaller 

 spermogonia in patches between the aecidia. These also arise from a 

 fungus mycelium in the cortex, whence the fungus was named Perider- 

 mium pini (var. corticola) . It is thus seen that the fungus P. pini was 

 regarded as a parasite of pines, and that it possessed two varieties, one 

 inhabiting the leaves and the other the cortex; the varieties were so 

 considered because of certain trivial differences found in the aecidia and 

 spermogonia. The disease may be popularly called 'Pine-blister.' " 



The fungus lives in the leaves of pines for a year or two before 



