1885. | G. M. Giles—On the Prothallus of Padina pavonia. (6) 
question. There are many points in connection with these bodies that 
require clearing up, but these can hardly be solved without continuous 
observation of the living plant. Like all surf-line weeds, Padina pavonia 
requires a very free supply of oxygen, and the conditions necessary for 
observing it in, if I may so speak, captivity are wanting on board ship ; 
so that the solution of these points must, I fear, be reserved for other 
observers more favourably situated. Assuming, however, that the body 
which has just been described is really the prothallus of this weed, it 
would render it extremely probable that all aleve producing “ spores’’ of 
but one kind gothrough some such cycle of changes; and a very large 
field of investigation appears in prospective as to the determination of 
the prothallus of each species. Some no doubt have been described as 
distinct species of algee, as, assuming their existence, they can hardly 
have been entirely overlooked up to now. 
EXPLANATION OF THE PLATES. 
Prater LV. 
Fig. 1. Padina pavonia, nat. size. The sori are disposed in concentric lines 
consisting of a structureless flattened indusial sac and a number of pear-shaped 
sporanges. Tufts of paranemata disposed along their sides give to the sori a woolly 
appearance. 
2. Vertical section of frond through a sorus showing sporanges and parane- 
mata, x 200. 
PLATE V. 
1. Prothallus of Padina pavonia, natural size. 
2. The same, x 10. 
» 98. Transverse section of same, x 20. 
4. Portion of the section shewing male tubes in oblique section, x 300. 
5. Male mother-cell containing danughter-cells producing red-pigmented 
rods, x 400. 
5, 6. Portion of the section shewing a female tube in transverse sec- 
tion, x 300. 
» 7 Adeniform tissne of lower surface of the prothallus containing 
“hedgehoe” cells in its meshes, x 300. 
» 8. One of the “hedgehog” cells more carefully drawn, x 500, 
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