Journal of Agricultural Research voi.xv 



Page 



Plate 52. Cronartium ribicola: A.— A section of a young telial column. B.— 

 A later stage in the development of the telial column. C— A longitudinal 

 section of a mature column. D.— Higher power view of the same section, 

 showing the arrangement of the individual spores, and the size of the nuclei. 

 E. — A cross section of a small mature column 660 



Plate 53. Cronartium ribicola: A drawing to show the intimate relation of the 



mycelium of the parasite to the host cells 660 



Plate 54. Cronartium ribicola: A.— A drawing of an infected 12-year-old main 

 stem. B.— Drawing of a section through part of a young aecium showing 

 the relation of tlie fertile cells with their denser protoplasmic contents to 

 the overlying sterile cells, in which the cytoplasm and nuclei have begim 

 to go to pieces 660 



Plate 55. Cronartium ribicola: A. — A drawing of a median section through a 

 very young uredinium. B. — A drawing of a median section through a 

 young uredinium, somewhat older than that illustrated in figure A. C. — 

 A drawing of a median section through a small mature uredinium 660 



Plate 56. Cronartium ribicola: A. — A drawing of the cell relations near the 

 edge of an secium to illustrate the formation of the multilayered secial perid- 

 ium. B. — A drawing of a section through a mature peridium, taken from 

 the same series as the photomicrograph in Plate 50, B. C. — A drawing of 

 a short mature telial column in which the teliospores (a) have germinated, 

 producing promycelia and sporidia (6) 660 



Plate 57. Cronartium ribicola: A. — A mature teliospore from the tip of a 

 colurmi. B. — A mature teliospore from the side of a column. C. — A ma- 

 ture teliospore from the side of a column. D. — Five germinating teliospores 

 from a longitudinal section of a column. E. — A germinating teliospore. 

 F. — Early prophase of the primary division in the promycelium. G. — 

 Late prophase of the primary division in the promycelium. H. — Early 

 anaphase of the primary division in the promycelium. I. — Later anaphase 

 than that shown in figure H. J, K. — Two anaphase stages of the primary 

 division. L. — Late anaphase of the primary division. M. — End of the 

 anaphase of the primary division. N. — The 2-celled promycelium. 

 O. — Metaphase of the second division. P. — Telophase of the second di- 

 vision. Q. — The reorganizing nuclei after the second division. R. — The 

 completed promycelium. S. — Surface view of a germinating promyce- 

 lium. T. — The tip cell of a germinating promycelium. U. — A little 

 later stage than the last. V. — Surface view of a tip cell of a promycelium 

 bearing a sterigma and a nearly mature sporidium. W. — A mature 

 sporidium. X, Y, Z. — Steps in the germination of the sporidia. AA. — 

 Sectional view of a mature sporidium. BB. — Sectional view of a germi- 

 nating sporidium. CC, DD. — Two stages in the formation of secondary 

 sporidia. EE. — Midanaphase of the division of the sporidium nucleus. 

 FF. — Late anaphase of the same. GG. — Sectional view of a binucleate 

 sporidium. HH. — Two cells from the vegetative mj^celium in the pine. 

 II. — A definitely polarized nucleus from the vegetative mycelium in 

 the pine, located just beneath the fertile layer of the young aecium 660 



Plate 58. Cronartium ribicola: A. — The elements of the pycnium. B. — An 

 active thin-walled haustorium from a pine host cell. C, D, E. — Old haus- 

 toria. F. — Telophase of division of one of the cells of the fertile layer to 

 form a sterile cell. G. — A newly formed sterile cell. H. — A large polarized 

 nucleus from the fertile layer. I. — An secial basal cell resulting from the 

 fusion of two adjacent cells of the fertile layer. J. — A diagram of a basal 

 cell resulting from the fusion of two cells from different levels. K. — ^A 



