PLATE 59 



Cronartium rihicola: 



A.— Germinating aeciospores. X 425. 



B. — Sectional view of the seciospore wall showing the manner in which the germ 

 tube is constricted. X 850. 



C. — A binucleate cell from the mycelium in a leaf of Ribes sp. The nuclei are 

 polarized as in the uninucleate mycelium. X 1,700. 



D. — A binucleate haustorium from a host cell of Ribes sp. X 1,700. 



E. — A uredinial basal cell. The nuclei are in prophase. X 1,700. 



F. — Metaphase of the primary division in the basal cell. The chromosomes are 

 visible as distinct units. X 1,700. 



G. — Early anaphase of the same division. X 1,700. 



H. — A later stage of the anaphase. X 1,700. 



I. — Final anaphase. The two groups at each pole are not clearly distinct in this 

 figure. X 1,700. 



J. — A binucleate urediniospore initial. The nuclei are polarized. X 1,700. 



K. — Metaphase or early anaphase of the division in the initial. X 1,700. 



L. — Late anaphase in the initial. The chromatin is condensing in two groups at 

 each pole. The second nucleus in the basal cell has been cut away. X 1,700. 



M. — Late anaphase group from the initial, for comparison with figure L. X 1,700. 



N. — A basal cell bearing a stalk cell surmounted by a nearly mature urediniospore 

 (a), and a secondary urediniospore initial {b). The nuclei in the latter are in pro- 

 phase. X 850. 



O. Metaphase of the secondary division in the basal cell, preparatory to the forma- 

 tion of a secondary urediniospore initial. X 1,700. 



P. A mature urediniospore. X 850. 



Q. A germinating urediniospore in sectional view. X 850. 



R. — A germinating urediniospore. X 425. 



S. — A telial basal cell. Both nuclei show centrosomes and polarization phenomena. 

 X 1,700. 



T. — Metaphase of the division in the telial basal cell. X 1,700. 



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



V. — Final anaphase of the same. X 1,700. 



W. — Telophase of the same. X 1,700. 



X. — A diagram of a telial unit column. Two young binucleate teliospores sur- 

 mount the basal cell. X 850. 



Y. — The two nuclei of the young teliospore just previous to fusion. Note the cen- 

 trosomes. X 1,700. 



Z. The two nuclei in the process of fusion. Two nucleoli and two centrosomes are 

 still visible. X 1,700. 



AA. — The large fusion nucleus. The chromatin is in heavy strands. X 1.700. 



BB. — The fusion nucleus, slightly decreased in size. The chromatin strands are 

 finer than in the preceding stage. X 1,700. 



CC. — The mature fusion nucleus. The chromatin is in the form of granules. X 

 1,700. 



