118 MR. H. M. WARD ON THE STRUCTURE, DEVELOPMENT, 
Fig. 41. Portion of thallus-margin, showing relation of radial rows of cells to the outline and zoospo- 
rangium. Gundlach 4. 
Fig. 42. A zoosporangium just before the emission of zoospores : on the upper surface is a circular hole, 
slightly elevated, through which the zoospores come out. Zeiss Е, ос. 4. 
Fig. 43. Portion of thallus with empty or nearly empty zoosporangia: а, seen from above; the two 
empty zoosporangia present slit-like openings; 0, from below; four zoospores were actively 
moving inside the sporangium, which is surrounded by rhizoids. Zeiss J, oc. 4. 
Fig. 44. Outlines of the upper surface of two zoosporangia, showing the double nature of the opening. 
The irregular slit in the upper membrane, the cuticle, discloses the round pore of the zoo- 
sporangium-wall beneath. Zeiss J, oc. 4. 
Figs. 45, 46, & 47. Zoospores in various stages after emission. Each comes out with rapid jerks, and is 
fusiform in shape; then it swings round and round, trailing one cilium, the body becoming 
more oval or subglobular ; finally it rounds off as it comes to rest, the cilia becoming coiled 
back on themselves and finally absorbed. Many swell and burst, scattering the brilliant 
granules. АП but one group imm. 4; ; the small group Zeiss D, oc. 4. 
Fig. 48. Group of young disks of the Alga. The smaller ones are zoospores some hours after coming to 
rest; in the larger specimens cell-divisions are already established. Imm. 75. 
Prate XXI. 
Fig. 47. For this series see above, Pl. XX. 
Figs. 49 & 50. Similar very young thalli, the cells of which have acquired the orange-red pigment in 
quantity; in very wet weather such specimens become green. Zeiss J, oc. 4. 
Figs. 51 & 52. Older specimens of thallus, showing mode of division of the cells ; in all these cases the 
division-walls are drawn exactly to scale as seen: a, Zeiss D, ос. 4; the rest, imm. 75. 
Fig. 93. Diagrams to illustrate the law of cell-division and growth followed by the RE С! the 
advances in complexity consist in bipartitions of the existing cells by vertical radial walls, followed 
by the insertion of tangential septa. The tendency of the new walls to abut on the old ones at 
angles approaching the vertical is remarkable. 
Fig. 54. Two zoospores of the Alga come to rest, have acquired an apple-green colour and thin mem- 
branous envelope, and are in process of being attacked by Fungus-hyphe developed from а 
spore. Such cases are common on Ше surfaces of leaves in wet seasons. Imm. +. 
Fig. 55. Zoospores come to rest, and becoming divided and invaded by a Fungus-hypha; several have 
already lost their coloured contents. Imm. 16. 
Fig. 56. An Alga-thallus attacked by the Fungus at an early stage; only five cells of the Alga retain 
their colouring-matter. The Fungus-hyphe are spreading, and have formed a dense mass of 
conidia. Imm. 4. 
Figs. 57 & 58. End of a branch and part of margin of an older thallus invaded by the Fungus; many 
cells have lost their contents, and become modified in growth, and the hyphe are now spreading 
around, branching and anastomosing опе with another. Fig. 57, Zeiss D, fig. 58, Е, 
Fig. 59. The fungus hyphz on the surface of the Alga, and spreading from its edges as it penetrates 
bereath. The hyphz follow very closely the divisions between the cells, especially the radial 
walls ; as they pass off their walls lose the dark colour. Imm. 15: 
Fig. 60. A pycnidium formed on the surface of the Algal disk, at the junction of many radiating hyphe ; 
several stylospores have escaped from the apical pore. Тһе orange-red colouring-matter is still 
seen in the cells, along the dividing walls of which the hyphz course. Zeiss E, ос. 4. 
Fig. 61. Portion of mycelium detached, showing the nature of the jointing, branching, and anastomoses. 
Imm. До: . 
