AND LIFE-HISTORY OF A TROPICAL EPIPHYLLOUS LICHEN. 117 
zoosporangia in the thallus. The outlines and relations of parts are accurately drawn; but 
the filling-up of the cell series in the thallus is somewhat diagrammatic. 
Figs. 17 & 18. Portions of Alga-thallus removed from the leaf and viewed from below in glycerine. The 
branched rhizoids are seen spreading in all directions from the under surface. Fig. 17, Zeiss D, 
oc. 4; fig. 18, part of same, Zeiss J, oc. 4. 
Fig. 19. Portion of edge of thallus, showing cuticle and thick-walled flattened rhizoids. Zeiss J, oc. 4. 
Fig. 19 a. Under view of a zoosporangium with three appressed rhizoids developed from sur- 
rounding cells. Zeiss J, oc. 4. 
Fig. 20. Barren hairs, showing their simple composition as rows of cylindrical cells, with orange-red 
contents. Zeiss D, oc. 4. 
Fig. 21. Two “ fertile hairs,” similarly constituted to the above, but with the apex developed into a tuft 
of zoosporangia, the base dilated and thickened. Zeiss D, oc. 2. 
Fig. 22. A tuft of zoosporangia, through which the axis of the “ fertile hair” has grown forwards and 
again formed a secondary tuft. Zeiss D, oc. 4. 
Fig. 28. Abnormally developed fertile hairs. In а the main axis had been broken off, and a side 
branch formed, the end of which proceeds to form a tuft; b, the end of the main axis, having 
formed the swelling, is prolonged forwards. Zeis D, oc. 4 
PLATE XX. 
Fig. 24. Normal development of the apex of the fertile hair to form the tuft of zoosporangia. The end 
swells up (а to c), and protrudes pairs of short branches (d), which then develope zoosporangia at 
their ends (е,/). The orange-red contents not depicted. Zeiss. D, ос. 4. 
Fig. 25. Base of “ fertile hair,” showing the lamellation of the very thick cell-wall. Zeiss J. 
Fig. 26. Cell from middle of a “ fertile hair," showing processes on inside of cell-wall. Zeiss E, ос. 4. 
Fig. 27. “ Barren hairs” of the thallus, to which fungoid hyphe and zoospores have become attached 
and are commencing to develope. Zeiss D. 
Figs. 28 & 29. The tuft of zoosporangia, showing origin and insertion of the supporting pedicels, and 
the annular attachment to the sporangia. Zeiss D. 
Fig. 30. A young zoosporangium on its curved pedicel; the sporangium already open by a terminal pore. 
Zeiss J. 
Fig. 31. More advanced zoosporangia, the contents of which are already broken up into zoospores, and the 
papilla formed : 0 was drawn one hour after а (in water); с, 12 hours later. Imm. 16. 
Figs. 32 & 33. Empty sporangia, from which zoospores have escaped. Zeiss J, oc. 4. 
Fig. 34. Nearly mature zoosporangia treated with HSO, and iodine ; the cell-wall swells and discloses 
laminz, and becomes coloured blue. 
Figs. 35 & 36. Emission of the zoospores from the ovoid sporangia; they come out singly and form 
groups. Each is а subgloboid orange-coloured body with two long cilia; many swell and burst 
(a) on coming to rest, scattering numerous colourless minute granules. 
Fig. 37. Group of zoospores come to rest; each rounds off, loses its cilia, and develops a membranous 
envelope and a nucleus-like body. Zeiss J. 
Fig. 38. Similar group just before coming to rest. Zeiss E, oc. 4. , 
Fig. 89. Portion of main body of Alga-thallus, showing radiating arrangements of cell series, and two 
young zoospórangia; each of the latter is the modified end cell of a series, and is filled with 
oily and granular orange-red protoplasm. Zeiss E, oc. 4. 
Fig. 40. Figures to illustrate the above more fully : а is accurately drawn as regards the cell-divisions ; 
b represents what would be if the cell series were laterally detached, a condition sometimes 
found naturally. а, Zeiss E, oc. 4. 
