PLATE 57 

 Cronartium ribicola: 



A. — A mature teliospore from the tip of a column. X 850. 



B. — A mature teliospore from the side of a coliunn. X 850. 



C. — A mature teliospore from the side of a column. X 850. 



D. — Five germinating teliosporesfrom a longitudinal section of a column. The 

 nucleus in the promycelium from the upper teliospore is in the telophase of the primary 

 division. X 850. 



E. — A germinating teliospore. The nucleus is about to pass through the germ pore 

 into the promycelium. X 850. 



F. — Early prophase of the primary division in. the promycelium. X 1,700. 



G. — Late prophase of the primary division in the promycelium. The chromatin is 

 in the form of complex tangle. X 1,700. 



H. — Early anaphase of the primary division in the promycelium. Eleven chromo- 

 somes are visible. X 1,700. 



I. — Later anaphase than that shown in figure H. Sixteen chromosomes visible. 

 X 1,700. 



J, K. — Two anaphase stages of the primary division. The chromosomes are well 

 advanced toward the poles. X 1,700. 



L. — Late anaphase of the primary division. The chromosomes are condensing into 

 deeply staining clumps, but the individuals are still discernible in some cases. 

 X 1,700. 



M. — End ot the anaphase of the primary division. The fibres connecting the two 

 chromatin groups are drawn to a thin fading strand. Note the radiations in the cyto- 

 plams in this and the preceding figure. X 1,700. 



N. — The 2-celled promycelium. X850. 



O.— Metaphase of the second division. X 1,700. 



P. — Telophase of the second division. Peculiar cytoplasmic radiations run from 

 the reorganizing nuclei. X 1,700. 



Q. — ^The reorganizing nuclei after the second division. X 1,700. 



R. — The completed promycelium. Each nucleus shows a small nucleolus and a 

 definite centrosome. X 850. 



S. — Stuface view of a germinating promycelium. X 850. 



T. — The tip cell of a germinating promycelium. The nucleus exhibits definite 

 polarization. X 1,700. 



U. — A little later stage than the last. The nucleus is passing into the sterigma on 

 its way to the sporidium. X 850. 



V. — Siu^'ace view of a tip cell of a promycelium bearing a sterigma and a nearly 

 mature sporidium. X 850. 



W. — A mature sporidium. The papilla marks the point of attachment of the 

 sterigma. X 850. 



X, Y, Z. — Steps in the germination of the sporidia. X 850. 



AA. — Sectional view of a mature sporidium. The nucleus shows polarization. 

 X 1,700. 



BB. — Sectional view of a germinating sporidium. The nucleus appears to be 

 moving toward the germ tube and preparing to divide. X 1,700. 



CC, DD. — Two stages in the formation of secondary sporidia. X 850. 



EE. — Midanaphase of the division of the sporidium nucleus. X 1,700. 



FF. — Late anaphase of the same. X 1,700. 



GG. — Sectional view of a binucleate sporidium. X 1,700. 



HH. — Two cells from the vegetative mycelium in the pine. X 1,700. 



IL — A definitely polarized nucleus from the vegetative mycelium in the pine, 

 located just beneath the fertile layer of the young aecium. X 1,700. 



