VIII Journal of Agricultural Research voi. xv 



Page 

 Plate 34. Cultures with greensand deposits: A. — Red clover. Potassium 

 supplied in greensand deposits from Red Bank, N. J. I, Series with green- 

 sand marl from upper stratum. II, Series with greensand from lower 

 stratum. B.— Turkey Red wheat. Potassium supplied in greensand 

 deposits from Red Bank, N. J. C— I, Turkey Red wheat. Potassium 

 supplied in greensand marl from Pamunkey Valley, Va. II, Red clover. 

 Potassium supplied in greensand marl from Pamunkey Valley, Va 492 



Seedling Diseases of Conifers 



Plate B. i. Normal damping-off on western yellow pine; caused usually by 

 Corticium vagum, Fusarium spp., or Pythium debaryanum. 2,3. Blacktop 

 damping-off on jack pine; probably caused by Trichoderma sp. 4. White- 

 spot injury, common type, on western yellow pine; usually due to excessive 

 heat at soil surface. 5. Whitespot lesion, one-sided type, on western yellow 

 pine; due to heat. 6. Late damping-off resulting from inoculation with 

 Pythium debaryanum on red pine more than 5 weeks old. 7. Wind injury 

 to jack pine 558 



Histological Studies on Potato Leafroll 



Plate C. Camera-lucida drawing of diseased tissues of the Irish potato: i. — 

 Tranverse section of an internal phloem group showing initial stage in for- 

 mation of intercellular spaces. 2. — Tranverse section of external phloem 

 and pericycle showing the same condition. 3. — Tranverse section of inter- 

 fascicular region of mature stem showing necrosis in xylem, cambium, 

 medullary ray cells, and cortex. 4. — Transverse section of external phloem. 

 5. — Transverse section of internal phloem of mature stem, showing severe 

 necrosis. 6. — Transverse section of internal phloem group, showing forma- 

 tion of a large intercellular cavity extending up to the protoxylem and 

 involving a few cells of the phloem 570 



Plate 35. A. — Normal potato plant, Paul Kruger variety, Ithaca, N. Y., 



March, 1916. B. — Potato leafroll in Paul Klruger variety 570 



Plate 36. Typical potato leafroll in Early Rose variety 570 



Plate 37. Typical potato leafroll in Paul Kruger variety 570 



Plate 38. A. — A cross section through upper part of stem, showing necrosis in 

 outer phloem and cortex. B. — Cross section through distal region of stem, 

 showing formation of intercellular spaces in outer phloem and cortex. C. — 

 Cross section through distal region of stem , showing formation of intercellular 

 spaces between the cells of the inner phloem. D. — View of another phloem 

 group showing cell wall thickening 570 



Plate 39. A. — Cross section through lateral bundle of petiole showing a 

 diseased phloem group in the internal region and the effect of necrosis on 

 the surrounding parenchyma. B. — Cross section of stem, showing an 

 unusual type of necrosis 570 



Plate 40. A. — Cross section of stem showing granular deposit in cell of cortex 

 and formation of intercellular spaces proceeding from the region of the 

 fibers centripetally. B. — Cross section of stem showing large schizogenous 

 cavity between cells of pericycle and cortex and centripetal advance of the 

 formation of intercellular cavities 570 



Plate 41. A. — Section of middle portion of stem showing necrosis in cells of 

 cortex and primary phloem. B. — Cross section of middle portion of stem 

 showing diseased areas in pericycle and outer phloem 570 



Plate 42. A. — Cross section of intemodal region of upper part of stem showing 

 radial stretching of the elements of the pericycle. B. — Longitudinal sec- 

 tion of nodal region of upper part of stem showing extent of necrosis 570 



