July i-Sept. 30, 1918 
Illustrations 
IX 
Plate 40. Flower pedicel and stem node of the potato: A.—Transverse sec- *age 
tion through pedicel of flower. B.—Portion of transverse section through 
node, lowing part of wing bundle of petiole above, part of stem bundle 
below, and leaf gap in center with connection of inner and outer phloem 
along the side of the stem bundle..— 25a 
Plate 41. Ontogeny of the potato; A.—Radial section of potato eye and part 
of mother tuber showing amount and position of procambium. B.—Trans¬ 
verse section through tip of potato stem, showing the general distribution 
of tissues, the amount of vascular tissue, and its arrangement into groups. 
C.—Transverse section through growing region of potato eye, showing the 
first visible differentiation of internal phloem groups. D.—Transverse 
section through tip of potato eye, showing the arrangement of the various 
parts and the beginning of vascular differentiation. 252 
Plate 42. Ontogeny of the potato: A.—Transverse section through potato sprout 
showing xnetaxylem and primary medullary rays. B.—Transverse section 
through part of growing region of potato sprout, showing position of the 
first formed protoxylem and the differentiation of the internal and external 
phloem groups from the procambium. C.—Transverse section through 
potato sprout, showing beginning of cambium development. D.—Trans¬ 
verse section through distal region of potato sprout, showing the first 
differentiation of internal phloem and protoxylem. 252 
Plate 43. Secondary growth of the potato: A.—Transverse section through 
nodal region of mature stem. B.—Transverse section through intemode 
of mature stem. C.—Transverse section through mature petiole.... 252 
PLATE 44. Secondary growth of the potato: A.—Transverse section through 
part of large stem bundle, showing type of xylem and medullary ray cells. 
B. —Transverse section through interfascicular region of mature stem, 
diowing the types of first and later formed secondary xylem elements. 
C. —Transverse section through part of mature root, showing secondary 
phloem. D .—Transverse section through part of mature petiole, showing 
secondary xylem. 252 
Plate 45. Secondary growth of the potato: A.—Transverse section through 
phloem of mature stem, showing most of the secondary elements to be 
sieve tubes and rays. B.—Transverse section through another region of 
mature stem, showing secondary phloem and rays. 252 
PLATE 46. Condition of the primary phloem in mature stems of the: potato: 
A.—Transverse sections through mature stem, showing primary phloem 
groups in interfascicular region. B.—Transverse section through the same 
region, showing primary internal phloem..... 252 
PLATE 47. Condition of primary phloem in mature stems of the potato: 
A.—Transverse section showing that most of the secondary phloem is made 
up of sieve tubes and ray cells. B.—Transverse section through mature 
stem, showing large internal phloem groups. 252 
Influence op Humidity upon the Strength and the Elasticity op 
Wool Fiber 
Plate 48. A.—A comer of the humidity room used to test wool fiber. B.— 
Records of the temperature and humidity during the experiment.__ .... 296 
Availability op Potash in Some Common Soil-Forming Minerals—Eppect 
op Lime upon Potash Absorption by Different Crops 
Plate 49. A.—Oats, showing growth with potash from various minerals, with 
and without calcium carbonate. B.—Soybeans, showing growth with 
potash from various minerals, with and without calcium carbonate. C.— 
Rye, showing growth with potash from various minerals, with and without 
calcium carbonate. D.—Cowpeas, showing growth with potash from 
various minerals, with and without calcium carbonate.. 316 
70396°—20 - 2 
