o6o 
Olive. — Sexual Cell Fusions in the Rusts. 
Fig. 21. Telophase of a double conjugate division in the Cicuta aecidium. The paiied 
arrangement of the four spindles i apparently only partially maintained. 
Fig. 22. Four reconstructing daughter-nuclei in a basal cell of Puccinia Cirsii-lanceolati . In 
three of the nuclei the centres still have an aggregation of chromatin about them. 
Fig. 23. Simultaneous multiple division in a multinucleated cell at the base of the aecidium of 
Puccinia Cirsii-lanceolati. Besides the nine poorly differentiated nuclei shown in the figure, three 
are to be found, belonging to this same cell, in the next section. No paired, or conjugate, relation 
of the nuclei is here apparent. 
Fig. 24. Simultaneous division of six nuclei (three more lie in a lower plane and are consequently 
not shown in the drawing) in a multinucleated cell at the base of the aecidium-cup of Uromyces 
Scirpi. The four upper mitotic figures show clearly the irregular mass of chromatin attached to one 
side of each central spindle. Here again no paired arrangement is apparent. 
Fig. 25. A multinucleated cell, from the base of the aecidium on the Thistle, x 960. 
(Figs. 26-40, showing sexual cell fusions, have been so oriented that the upper part of each 
figure points toward the top of the plate as toward the epidermis of the host.) 
Fig. 26. Two pairs of fusing cells. Above the upper gamete of the right pair is a ‘ sterile cell ’. 
Fig. 27. Fusion of two cells, and the apparent migration of one nucleus over into the right half 
of the ‘ fusion cell ’. A large degenerating sterile cell has been cut off from the tip of the right 
gamete. 
Fig. 28. Cell fusion, in which the lower of the two gametes apparently arises from a hypha 
which comes up obliquely toward the eye. A budding growth has pushed out above, to one side of 
the sterile cell, before the passage of the lower nucleus into the upper part of the fusion cell. 
Fig. 29. Basal fusion cell, showing, below, the remnant of the absorbed partition wall which 
formerly separated the two gametes. One spore ‘ mother-cell ’ has been budded off and a second 
bud has started off to the left. A detached, crushed sterile cell lies between the two buds; 
whether this originally tipped the upper of the two gametes is uncertain. 
Fig. 30. The partially-absorbed partition wall which once separated the two gametes is here 
seen to be peculiarly bent and contorted. 
Fig. 31. One gamete appears to He obliquely below the upper gamete, and the absorption of 
the wall separating them has apparently just begun. The upper gamete bears an unusually large 
sterile cell, the contents of which, excepting the nucleole, appear to have almost entirely degenerated. 
Fig. 32. Fusion cell in which the conjugation pore is clearly shown. The two conjugate 
nuclei have entered upon the prophases of division, as evidenced by the fact that one nucleus has 
cast out its nucleole and left it. behind in the lower gamete. 
Fig. 33. An instance of cell fusion in which the nucleus of the lower gamete has just begun to 
pass through a very small pore into the upper gamete. 
Fig. 34. A similar instance, in Gymnoconia interstitialis , in which more than half of the lower 
nucleus has passed through a small conjugation pore. The conjugating hyphae are evidently 
obliquely placed with respect to each other. 
Fig. 35. Cell fusion in Gymnoconia in which the two conjugating cells lie side by side and 
parallel to each other. One has grown up a little higher than the other. A dense, finely granular 
aggregation of protoplasm lies in the fusion cell where the conjugation pore was formed. The 
centrosome of each nucleus is dumbbell-shaped and is in process of division. 
Fig. 36. A similar fusion cell in Gymnoconia , from the same preparation as the one shown in 
Fig. 34- 
Fig. 37. The beginning of the formation of the conjugation pore in Phragmidium potentillae- 
canadensis. A deeply staining body, somewhat similar to a nucleole, lies in the pore. 
Fig. 38. Fusion cell in Phragmidium potentillae-ccnadensis, which has begun to grow out to 
one side of the sterile cell. 
Fig. 39. Fusing tips of two hyphae of the micro-form, Puccinia transform ans. Excepting for 
their nucleoles, the two nuclei are poorly differentiated. 
Fig. 40. Cell fusion in Puccinia transformans, in which an end cell of one hypha has fused with 
a penultimate cell of another hypha. 
