Nov. 15, 1920 Hypertrophied Lenticels on the Roots of Conifers 255 



one of these hypertrophied lenticels on a root of Pinus rigida. The out- 

 growths consist of homogeneous parenchymatous elements, more or less 

 radially elongated, sometimes very much so. The individual cells are 

 thin-walled with a thin layer of cytoplasm. 



SPECIES AFFECTED 



Stahl (i<?) states that all trees which have lenticels on the stems also 

 have them on the roots. De Vaux (5) reports the presence of lenticels 

 on the roots of a large number of tree species, including a number of 

 conifers. For one species of Ephedra he states that lenticels are found 

 only on the roots. He states that especially in Pinus maritima the 

 lenticels on the roots are larger than those on the stems. This author 

 was able to find or to produce lenticel hypertrophy on some part of the 

 plant in 60 per cent of the 155 plant species considered but was unable 

 to secure any hypertrophy on the representatives of the several conif- 

 erous genera which he studied. On roots less than 3 mm. in diameter 

 he found the normal lenticels so small that the microscope was usually 

 necessary in demonstrating them. Tubeuf (20) lists a small number of 

 species, of which he was able to secure lenticel hypertrophy on some part 

 of 12 nonconifers. He, however, failed to get this hypertrophy on 

 species of Sequoia, Thuja, and Taxus, or on Gingko biloba and 14 other 

 nonconifcrous species. Zach (23) later secured hypertrophy of lenticels 

 on stems of G. biloba under certain conditions. However, a rather 

 careful search in the earlier literature appears to justify the statement 

 by the reviewer of Zack's paper (16) that no hypertrophy of lenticels 

 had been up to that time reported on conifers. 



The present writers have found hypertrophied lenticels on the roots of 

 the following conifers : Pinus ponderosa, Pinus coulteri, Pinus rigida, Pinus 

 resinosa, Pinus banksiana, Pinus virginiana, Pinus syhestris, Pinus cari- 

 baea, Pinus strobus, Pinus monticola , Pinus excelsa, Picea canadensis , Picea 

 rubens, Picea mariana, 1 Picea pungens, Abies balsamea, 2 Tsuga canaden- 

 sis, Larix laricina, Taxus cuspidata, Taxus brevifolia, and Araucaria 

 bidwellii. 



Several of the species of Pinus on which the hypertrophy was found 

 were growing in the greenhouse of the United States Department of 

 Agriculture at Washington, D. C. It was noteworthy that plants of 

 Juniperus virginiana under the same conditions in the same greenhouse 

 apparently were free from such growths so far as could be determined. 

 In a swamp in which the hypertrophied lenticels were found on Abies 

 balsamea, Picea rubens, and Tsuga canadensis none could be discovered 

 on Taxus canadensis. Among the pines the hypertrophied lenticels 

 were frequent mainly on the 3-needled species, Pinus ponderosa and Pinus 



1 Material furnished by Dr. H. P. Brown, of The New York State College of Forestry at Syracuse 

 University. 



2 Dr. James R. Weir advises the writers that he has frequently found hypertrophied lenticels on the 

 rcots of Abies grandis in the Northwest. 



