552" SUMMARY OF CUBKENT RESEARCHES RELATING TO 



is divided very rapidly into a number of cells whose arrangement can 

 still be followed even in quite old protballia. The rudiments of the 

 archegones make their appearance very much as in Marattiaceje ; the 

 neck being first formed by periclinal division, then the neck-canal-cell ; 

 and finally the ventral canal-cell is cut oif from the oosphere, when the 

 canal-cells thrust themselves between the neck-cells. 



Antherozoids of Ferns.* — M. L. Guignard has investigated the mode 

 of development of the antherozoids in a number of genera of ferns, viz. 

 Adiantum, Gymnogramme, Pteris, Pellea, Asjndium, and Asplenium be- 

 longing to the Polypodiacese, Osraunda among the Osmundaceae, and 

 Anginpteris among the Marattiacese. 



The processes are, in all essential points, identical with those in the 

 Characeast and Muscinese. The antherozoids are larger than those of 

 the Muscineae, and are provided with a larger number of cilia ; they 

 proceed from rounded or ovoid mother-cells. The nucleus transfers 

 itself, before it becomes transformed into an antherozoid, from a central 

 to a lateral position. The mature antherozoid consists of from two to 

 three turns of the spiral ; its anterior extremity has the form of a beak ; 

 this portion being comparatively thin, the posterior portion thicker; 

 the latter carries, when the antherozoid escapes, a vesicle which contains 

 starch-grains and the residue of the nutritive protoplasm. The forma- 

 tion of the cilia takes place at an early period ; the hyaline layer of 

 protoplasm which covers the outer surface of the nucleus developes into 

 an annular band inclosing the granular protoplasm. This layer is more 

 extensive than in the lower Cryptogams, corresponding to the greater 

 number and length of the cilia. The formation of these latter commences 

 at the anterior end of the antherozoid, and is rapidly completed along 

 their whole length, which somewhat exceeds that of the adult body. 

 They are inserted in a tuft on the anterior half of the first turn of the 

 spiral. 



Stem of Ferns.J — M. Leclerc du Sablon describes the difference 

 between the structure of the root and the stem in Pteris aqiiilina. These 

 results agree in all essential points with those obtained by M. Gerard in 

 Asplenium striatum and A. cuneatum. Near the base of the stem the 

 smaller vessels of the wood lie towards the exterior, as in the root, 

 but this arrangement is somewhat altered by the insertion of the leaves. 

 The central cylinder of the stem is formed by a xylem-portion at the 

 centre, a ring of phloem round the xylem, and a layer of j)ericycle round 

 the phloem. Soon this structure is somewhat modified. Towards the centre 

 of the xylem-portion phloem-elements appear, and this phloem gradually 

 increases. In the stem there is then at the centre the phloem, then a 

 ring of xylem, then a ring of phloem, then the pericycle. A comparison 

 has been made between the stem of Ferns and that of Auricula ; in all 

 these plants the thickening of the stem is not effected by secondary 

 formations, but by successive divisions of the central cylinder. The 

 same general results were presented by other ferns, 



Varieties in Ferns.§ — Mr. E. J. Lowe has observed, in the case of 

 Scolopendrium, that the same prothallium will sometimes produce two 



* Comptes Eeiidus, cviii. (1889) pp. 464-6, and Kev. Gen. de Bot. (Bonnier), i. 

 (1889) pp. 71-8 (1 pi.). t Of. this Journal, ante, p. 417. 



X Bull. Soc. Bot. France, xxxvi. (1889) pp. 12-4. 

 § Ami. of Bot., ill. (1889) p. 129. 



