372 Blackman. — On the Fertilization , Alternation of 
Fig. 56. Later stage than above, showing chromatin separating into two daughter-masses, 
x 1900. 
Fig. 57. Division in spermatial hypha in which chromatin shows a longitudinal division into 
two masses, x 1900. 
Fig. 58. Very young spermatia with chromatin still an almost solid mass, x 1900. 
Fig. 59. Group of mature spermatia. x 1900. 
Figs. 60-65. Aecidium-development in Phrag. violaceum . 
Fig. 60. Peripheral portion of young aecidium, showing the simplicity of structure. On the 
extreme left the special cells developed beneath the epidermis of the leaf are still undivided, while 
towards the middle a distinction into fertile and sterile cells can be observed and some of the fertile 
cells have already become binucleate. On the right the division of the fertile cells and the formation 
of aecidiospores and intercalary cells can be seen ; the epidermis at this part has been ruptured by 
the development of the aecidiospores. x 340. 
Fig. 61. Small portion of young aecidium, showing epidermal cells of leaf, sterile cells and 
fertile cells. Two of the fertile cells have become binucleate and one is still uninucleate ; the one 
on the right has begun to grow up and push through the sterile cell, x 1350. 
Fig. 62. Fertile cell with two nuclei of dissimilar structure, x 1350. 
Fig. 63. Portion of aecidium showing fertile cell with nuclei of unequal size and different 
structure ; the nuclei of the sterile cells have become partly disorganized, x 1350. 
Fig. 64. Similar to above, x 1350. 
Fig. 65. Fertile cell showing small densely staining nucleus in contact with larger nucleus with 
well-marked nucleolus, x 1350. 
PLATE XXIII. 
Figs. 66-77 a • Aecidium-development of Phrag. violaceum , continued. 
Fig. 66. Portion of young aecidium, showing nucleus of cell (basal cell) below one fertile cell 
migrating into another fertile cell. Epidermis of leaf seen above and mesophyll below, x 1350. 
Fig. 67. Similar stage to above, but sterile cells are empty, x 1350. 
Fig. 68. Nucleus of basal cell migrating into fertile cell immediately above, x 1350. 
Fig. 69. Very early stage of migration, x 1350. 
Fig. 70. Late stage of migration ; the distinction between the two nuclei very clear, x 1350. 
Fig. 71. Fertile cell which has cut off the first aecidiospore-mother-cell. x 1050. 
Fig. 72. Division of paired nuclei (conjugate division) in the first cell cut off from the fertile 
cell, x 1050. 
Fig. 73. Later stage, in which the nuclei of the one aecidiospore and the intercalary cell are 
constituted, but no wall is yet formed between them, x 1050. 
Fig. 74. Cell-row of aecidium showing, from above downwards, young aecidiospore, intercalary 
cell, aecidiospore-mother-cell, and fertile cell. x 1050. 
Fig. 75. Mature aecidiospore. x 1050. 
Fig. 76. Abnormal trinucleate fertile cell which has cut off a trinucleate aecidiospore-mother- 
cell. x 1050. 
Fig. 77. Fertile cell with three nuclei undergoing triple conjugate division ; the three solid 
masses of chromatin and the three nucleoli are to be seen, x 1050. 
Fig. a. Sterile cell which has grown up between two epidermal cells, x 1350. 
Figs. 78-84. Uredospore-development of Phrag. violaceum. 
Fig. 78. Group of developing uredospores on perennial mycelium, from stem of Rubus\ four 
basal cells are marked x . x 600. 
Fig. 79. Group of basal cells from which the stalked uredospores will be developed, x 1000. 
Fig. 80. Basal cell with young uredospore-mother-cell . x 1000. 
Fig. 81. Young uredospore-mother-cell. x 1350. 
Fig. 82. Uredospore-mother-cell dividing to form uredospore and stalk-cell, x 1350. 
Fig. 83. Young uredospore with stalk-cell, x 1350. 
Fig. 83 a . Portion of uredospore and stalk-cell to show protoplasmic continuity between the 
two. x 1350. 
Fig. 84. Mature uredospore, showing the two nuclei of an irregular shape, x 800. 
Figs. 85-87. Teleutospore development in Phrag. violaceum. 
