256 Journal of Agricultural Research voi.xx,No. 4 



rigida, while on the strictly 2-needled Pinus mrginiana, Pinus banksiana, 

 and Pinus resinosa they were very difficult to find. Klebahn (io,p. 582, 

 586) states that up to the time of his publication he had not been able to 

 find lenticels on Pinus sylvestris, nor had he satisfactorily demonstrated a 

 substitution for lenticels. 



Excrescences like those just described on the conifers are common 

 and widespread occurrence on a number of dicotyledonous plants, 

 particularly upon swamp plants such as Sambucus canadensis , Rhus 

 copallina, Decodon verticillatus , and Cephalanthus occidentalis . Such 

 excrescences on dicotyledonous plants have long been known under the 

 term ' ' water lenticels. " 



CONDITIONS UNDER WHICH HYPERTROPHY HAS BEEN FOUND 



The lenticel hypertrophy observed on roots has been generally limited 

 to plants growing in wet soil. Affected hemlock, balsam fir, red spruce, 

 and black spruce have already been noted as growing under swamp 

 conditions. All the pitch pines found with hypertrophied lenticels in 

 the vicinity of Washington were in heavy, wet soil. There hypertrophy 

 was very frequent on Pinus rigida and P. mrginiana growing in 

 swampy locations. The pines found so affected in the greenhouse at 

 Washington were all growing in soil very much wetter than that in which 

 they are usually found. The only Scotch pines found with hypertrophied 

 lenticels were growing at the edge of an irrigation ditch in especially 

 wet soil at a Michigan nursery. The same has been true in the most 

 striking cases of hypertrophy at the Bessey Nursery. In a bed, a portion 

 of which was repeatedly flooded from a leaking irrigation ditch, approxi- 

 mately 20 per cent of the plants showed marked cases of hypertrophy, 

 while less than i^ per cent of the plants showed hypertrophy in parts 

 of the neighboring beds which were not affected by the leakage. Infor- 

 mation has been received from Mr. W. H. Schrader that at the Monu- 

 ment Nursery of the United States Forest Service in Colorado the only 

 conspicuous occurrence of root lenticel hypertrophy was during an 

 unusually wet season. The hypertrophy here considered has been found 

 both in heavy and in very sandy soils; in the latter case there was ap- 

 parently more hypertrophy in parts of the beds to which clay had been 

 added. 



The youngest seedling observed with lenticel hypertrophy was one 

 of Pinus ponderosa which was raised from the seed with its roots in a 

 2-ounce bottle of tap water in the laboratory. This water was not 

 changed during the entire period of growth. The bottle was stoppered 

 but was not absolutely sealed at the point of passage of the stem through 

 the stopper. At the end of approximately five months the plant, which 

 still seemed fairly vigorous, had developed a single root, which, after 

 reaching the bottom of the bottle, had coiled itself around two or three 

 times close to the peripheral limit of the bottle. On this tap root were a 



