ZOOLOGY AND BOTANYj MICROSCOPY, ETC. 277 



segments does not take place so regularly as in the apex of Equisetum, 

 60 that in good preparations only two circuits, or the six youngest 

 segments, could be followed ; these were more often found running to 

 the left than to the right. In Polypodium vulgare each internode 

 has the rudiment of a lateral shoot ; and in P. Heracleum, with the 

 leaves arranged in a single row, the author found sometimes two 

 rudiments, one on the right, the other on the left side of the same 

 internode. But these rudiments do not all develope together ; most 

 of them remain in a dormant condition. They originate from a super- 

 ficial cell at the growing point of the stem, at a great distance from 

 the origin of the leaf, and at a considerable greater angle of diverg- 

 ence as respects the vertical plane of symmetry. There cannot be 

 any genetic connection between the shoot and the leaf; those ferns 

 which were examined could not be brought under the scheme of 

 axillary branching. 



In all the species examined the leaves originate from a superficial 

 cell distinguished by a stronger swelling of its outer cell-wall, which 

 divides by two septa curved towards one another in parabolic curves, 

 between which the two-edged apical cell of the leaf is formed. It 

 arises far behind the apical cell of the stem, for it can be recognized 

 only in the fourth or sixth segment ; but in Pteris sometimes in 

 the third. The author was able to determine that every segment of 

 the two dorsal rows in PolypocUum vulgare forms a leaf. When from 

 two to six leaves, including rudiments, develope in the year, the apical 

 cell of the stem can divide, during the same time, only from three to 

 nine times ; and perhaps not half so often in Pteris aquilma ; but this 

 could not be absolutely determined, since in this fern each leaf takes 

 four years to develope. 



In all ferns the intensity of growth and the rapidity of division of 

 the apical cell of the stem are extremely small ; and on these points 

 the following results were obtained. At the growing point, in 

 the first three or four segments, the average absolute growth increases 

 regularly from the apical cell, the relative growth decreases. The 

 change in the intensity of growth varies greatly in the same species 

 during the same time and at the same age of the youngest segment in 

 different individuals. The segments separated from one and the same 

 apical cell in the growing state frequently differ greatly in size ; while 

 equal segments behave very variously as respects the intensity of growth 

 in successive sections. 



The above facts are stated by the author in two tables. Starting 

 from the superficial view of the growing point, the outlines of the seg- 

 ments were drawn on paper under a magnification of 280 diameters. 

 These drawings were then laid on plastic clay, and successive apical 

 cells and segments cut out and weighed ; the proportion of the weights 

 thus obtained giving that of the volumes of the cells. 



Prothallinm of Lycopodium.* — M. Treub gives an exhaustive 

 account of the prothallinm of Lycopodium cernimm from artificial and 



* Ann. Jard. Bot. Euitenzorg, iv. (1884) pp. 107-38 (9 pis.). See Mr. W. 

 T. Thiselton Dyer in ' Nature,' xxxi. (1885) p. 317. 



