ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 371 



nised. Spore formation and chromosome reduction are completed by 

 about the middle of April. 2. In the resting nucleus is a large deeply 

 staining nucleolus ; the nuclear reticulum is very fine and contains 

 little or no chromatin. 3. Each original archesporial cell gives rise to 

 8, 16 or 32 spore-mother-cells. As division approaches the nucleolus 

 disappears, bands of chromatin are differentiated, and the spireme is 

 formed. 4. The spireme divides transversely into twelve chromosomes 

 of nearly equal size. No centrosomes are present. 5. The chromo- 

 somes split longitudinally, and the halves retreat from the equatorial 

 plate towards the poles. The telophase is normal ; several nucleoli are 

 formed, but fuse into one. 6. The wall dividing the daughter-cells is 

 formed at the equatorial plate. 7. The resting nucleus of the newly 

 formed spore-mother-cell resembles that of the pre-meiotic cells, but 

 contains more chromatin. A budding off from the nucleolus occurs. 

 8. The spireme then differentiates out slowly and gives rise to the 

 first contraction figure. 9. On emergence the spireme is shorter and 

 thicker ; a network is formed and is followed by a second contraction, 

 with loops in the spireme, which now shows traces of longitudinal fission. 

 10. The chromosomes are formed of local aggregations of chromatin 

 and still show traces of longitudinal fission. They remain in the centre 

 of the cell, while the nucleolus passes into the cytoplasm and soon 

 disappears. 11. No centrospheres are found at the poles of the spindle. 

 The chromosomes, six in number, become arranged on the equatorial 

 plate, and show the characteristic and X forms. They divide trans- 

 versely and pass to the poles. 12. The homotype division results in 

 the formation of four nuclei, which are later found in the spores. 



Discharge of Antherozoids in Hepatics.* — A. S. Home describes 

 the discharge of antherozoids in Fossombronia and Haplomitrium 

 Hookeri. He shows that the following processes take place during 

 ripening of the antheridium : — 1. Change in character of the chlorophyll 

 corpuscules of the wall from above downwards. 2. Local degeneration 

 of the middle lamella in the wall of the antheridium. Cell filaments 

 are formed in Fossombronia. Special cells rise in Haplomitrium. 3. The 

 upper wall- cells become free from the limiting membrane of the wall. 

 When the antheridia are ripe, dehiscence takes place, the tense wall 

 rupturing upon access of water. 



Dislike of Sphagnacese for Lime.| — H. Paul discusses the cause of 

 the dislike shown by Sphagnaceae for lime. Despite what has been 

 written about the matter, it is not calcium sulphate but calcium 

 carbonate to which the Sphagnacege are so sensitive. The acidity of 

 these mosses is greatest in those that are strictly confined to elevated 

 moors, and least in those of the plains. The acid serves for dissolving 

 nutritive substances. It is present in quantity where little air-borne 

 nutritive matter reaches the plants ; and such plants are very sensitive 

 to the neutralisation of their acidity by lime. The acidity and the 

 sensitiveness to neutralisation diminish in proportion as the amount of 

 available mineral matter increases. S. rubeUum, however, requires an 



* Ann. of Bot.,' xxiii. (1909) pp. 159, 60 (figs.). 



t Mitt. k. bayr. Moorkult. ii., pp. 63-118 (2 pis.). See also Hedwigia, xlviii. 

 (1908) Beibl., p. 111. 



2 C 2 



