772 REPORT— 1887. 



Pandorinn coeiioliium, or by divisiou to several spores, each of ^Yllich gives rise to a 

 sexual Pandorina ccenobium. 



Upon these compaiisous it is suggested that alternation of generations arose 

 from polyemhryony, not, as according to Pringsheim's theory, by a process of dif- 

 ferentiation from a number of individuals which were both sexual and asexual. 



If this hypothesis is true it is then pointed out that the sporophyte, as it is more 

 generally known in the mosses and higher plants, is a )iew body originating among 

 the higher Algse and lower Liverworts not genetically connected with the sexual 

 body. Consequently the tissues of the sporophyte cannot be homologous with those 

 of the oophyte, but ma}' be analogous. 



The Floridea and Characece receive special consideration. 



2. On a Curious Habitat of certain Mosses. Bj C. P. Hobkikk, F.L.S. 



The author exhibited specimens of two purely terrestjial mosses, Mnium 

 hornum and Poli/trichmn coiinmnie, wjiich he had found growing in a quarry pool 

 near Dewsbury ^West Riding of Yorkshire), quite submerged, and apparently of 

 some years' growth. The only difierence from the normal type was in the attenua- 

 tion and elongation of the stems, the cell structure both of stem and leaves being 

 unaltered. 



3. Report of the Peradeniya Committee. — See Reports, p. 96. 



4, On the Constitution of Cell-walls and its Relation to Ahsorption in 

 Mosses} By J. Reynolds Vaizey. 



POLTTEICHUM CoMlITJNE, LiNN, 



I. Cell-walls of Spm-opht/te. — (1) Transverse section placed in iod. chlor. zinc ; 

 walls of epidermal cells brownish-yellow, rest of the cells more or less blue, the 

 hypodermal sterome even slightly bluish in tint. 



This is the case in both seta and apophysis. The guard-cells of Stomata on 

 apophysis have a delicate cuticle well seen with iod. chlor. zinc ; the internal part 

 of cell-wall is pure cellulose, being turned blue with iod. chlor. zinc. 



Chromic acid (strong) dissolves all the tissues more or less I'apidly, leaving 

 behind only the delicate cuticle, which is then distinctly seen as a membrane isolated 

 from the tissues. The cuticle is dissolved by boiling in strong potash: is made dis- 

 tinctly visible and frequently partially separated from epidermis by chlorate of 

 potash and nitric acid. 



Anniline chloride + HCl turns the hypodermal sterome from brown to orange- 

 yellow. 



(2) Water is only absorbed by foot of seta. Water placed on capsule, apophysis 

 or seta goes off as from an oily surface. 



II. Cell-xcalh of Oophyte. — (1) Iod. chlor. zinc central strand of cells only 

 turned blue. 



Chromic acid not quite concentrated rapidly dissolves all the ti.ssues ; no trace 

 of a cuticle or any cuticularised cell-walls to be seen. 



Anniline chloride + IICl turns all peripheral tissues orange-yellow. 



(2) Water sticks to leaves and stems, and is rapidly absorbed by them, as may 

 be easily seen if only a few drops of water are left on the stem and leaves after 

 immersion in water ; after a few minutes it has all disappeared. A withered stem ; 

 placed in water, head foremost, it rapidly revives. 



Hence it is seen that the seta and apophysis of sporophyte is cuticularised, and 

 consequently gases only can be absorbed by those structures, and water is (as I 

 have shown elsewhere) only absorbed by 'the foot. In the oojjhyte there is no 

 cuticle, and consequently water can be, and is, absorbed by both stems and leaves. 



' See also Annals of Botany, vol. i. No. 2. 



