310 BULLETIN No. 189 [June, 



ALTERNANTHERA, Telanfhera sp. 



In the fall of 1912 cuttings from alternanthera, coleus, and salvia 

 plants which had been placed in the same bench were found to be 

 damping-off. A microscopic observation and pure cultures from dis- 

 eased cuttings showed that Rhizoctonia Solani was the causal organism. 

 Later the fungus was found on alternanthera plants in the field, but 

 apparently it caused no injury there. 



Alternanthera plants grow low and bushy, and thruout the sum- 

 mer, no matter how dry the season* the soil underneath is usually 

 moist. On close examination of the tangled mass of branches, strands 

 of a fungus, which were later found to be made up of bundles of 

 hyphae, could be seen spreading in all directions. At first glance the 

 masses of mycelium looked very much like old spider webs. A number 

 of different varieties of alternanthera were examined, and all were 

 found to have the characteristic brown strands ramifying upon the 

 surface of the whole under side of the plant. The reddish varieties 

 seemed to have more of the fungous strands than did the green and 

 variegated plants. Cultures from the brown strands in every case 

 yielded pure cultures of Rhizoctonia which corresponded morphologi- 

 cally and physiologically to the Rhizoctonia obtained from the cut- 

 tings. 



Whether the fungus was at any time parasitic on the plants in the 

 field was questionable. However, cuttings made from them still con- 

 tained pieces of mycelium, and when placed in sand in the greenhouse, 

 the fungus did parasitize not only the alternanthera cuttings but others 

 as well. 



The belief that Rhizoctonia is present on the branches of the alter- 

 nanthera plant thruout the year was corroborated in 1913 and again 

 in the fall of 1914, when the cuttings made from plants in the field 

 began to damp off in the cutting bench. Repeated observations showed 

 that the fungus was present on the plants in the field, notwithstanding 

 the fact that they had been planted in new soil. Old plants brought 

 in from the field were cut close to the roots and planted in flats in the 

 greenhouse. These sprouted and developed new shoots, from which 

 cuttings were made. Many weeds came up in the flats during the win- 

 ter, and in March both the cuttings and the weeds became infected 

 with Rhizoctonia. It seems, therefore, that the fungus is present on 

 alternanthera at all times of the year, tho the only injury it causes is 

 damping-off of cuttings in the greenhouse. 



ALYSSUM, SWEET, Alyssum odoratum 



During June, 1914, when the bedding and decorative plants were 

 being set out from the floricultural greenhouses of the Station, about 



