298 Welsford.—Nuclear Migrations in Phragmidium violaceum . 
3 . Christman, A. H.: Sexual Reproduction in the Rusts. Bot. Gaz., vol. xxxix, 1905. 
4 . —- The Alternation of Generations and the Morphology of the Spore Forms 
in the Rusts. Bot. Gaz., vol. xliv, 1907. 
5 . - The Nature and Development of the Primary Uredospore. Trans. Wis. 
Acad. Sc., vol. xv, 1907. 
6. Dittschlag, E.: Zur Kenntnis der Kernverhaltnisse von Puccinia Falcariae. Centralbl. Bakt., 
xxviii, 1910. 
7 . Fraser, H. C. I. : On the Sexuality and Development of the Ascocarp in Lachnea stercorea . 
Ann. of Bot., vol. xxi, 1907. 
8. Fromme, F. D. : Sexual Fusions and Spore Development of the Flax Rust. Bull. Torr. Bot. 
Club, vol. xxxix, 1912. 
9 . - The Morphology and Cytology of the Aecidium Cup. Bot. Gaz., vol. Iviii. 
I 9 I 4 - 
10 . Grove, W. B.: The British Rust Fungi. Camb. Univ. Press, 1913. 
11 . Hoffmann, A.: Zur Entwicklungsgeschichte von Endophyllum sempervivum. Centralbl. Bakt., 
xxxii, 1912. 
12 . Kurssanow, L,: Zur Sexualitat der Rostpilze. Zeitschrift fur Botanik, ii, 1910. 
13 . Olive, E. W. : Sexual Cell Fusions and Vegetative Nuclear Divisions in the Rusts. Ann. of 
Bot., vol. xxii, 1908. 
14 . Pavolini : L’Ecidio della Puccinia fusca. Bull. Soc. Bot. Ital., 1912. 
DESCRIPTION OF PLATE XVI. 
Illustrating Miss Welsford’s Paper on Phragmidium violaceum. 
Fig, 1. Migration of nucleus. The sterile cell has been cut away, x 1,300. 
Fig. 2. Migration of nucleus between the cells of separate hyphae. x 1,300. 
Fig. 3. Ditto, x 1,300. 
Fig. 4. Migration of nucleus from vegetative cell to fertile cell immediately above it on the 
same hypha. x 1,300. 
Fig. 5. Ditto, x 1,300. 
Fig. 6. Migration of nucleus from vegetative cell of one hypha to fertile cell of another, x 1,300. 
Fig. 7. Ditto, x 1,300. 
Fig. 8. Ditto. In this case the nucleus is passing through a very large pore between two 
hyphae. x 1,300. 
Fig. 9. Ditto. The nucleus passing through a large pore between two cells of the same hypha. 
x 1,300. 
Fig. 10. A binucleate cell showing the pore through which the nucleus has passed, x 1,300. 
Fig. 11. A binucleate cell showing the pore through which the nucleus has passed, x 1,300. 
Fig. 12. Semi-diagrammatic drawing of a young aecidium (peripheral region). The fertile 
cells are uninucleate, and no empty cells can be seen, x = host cells, x 500. 
Fig. 13. Semi-diagrammatic drawing of the same aecidium as that shown in Fig. 12, but in 
the median region. Here the fertile cells have become binucleate and empty cells can be seen near 
their bases, x = host cells ; e = empty hyphal cells, x 500. 
Fig. 14. Semi-diagrammatic drawing of a nearly mature aecidium, showing the young aecidio- 
spores, the binucleate fertile cells, the layer of empty cells, and the uninucleate hyphae ramifying 
amongst the host cells, x 500. 
