336 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the segmentation of the apical cell. The first stolon's rudiment appears 



alter the third or fourth leaf of the embryo. The firsi lateral axes of 

 the embryo Nephrulfpis are in function root-bearers. The stolon, like 

 the leaf, is the product of a special segment of the apical cell. The tir-i 

 stolons of epiphytic species serve to anchor the plant, and are very 

 hydrotropic. 



Physiological Sheaths in Ferns.* — P. Basecke publishes detailed 

 results of his studies upon the physiological sheaths of the axes and 

 fronds of the Filicineae, and upon the substitution of cork. He dis- 

 cusses the endodermis at great length from the points of view of 

 development, structure, biology, and physiology. He then treats of the 

 formation of cork, the dividing layers between rhizome and frond, the 

 lenticels and the intercellular cuticularisation, the mechanical tissues 

 of rhizome and frond, and their lignification. He appends a long 

 bibliography. 



Revision of the American Species of Dryopteris.f — C. Christensen 

 having, when preparing his " Index Filicum," realised the extremely con- 

 fused condition in which the numerous forms allied to the two species, 

 Dryopteris opposita and D. Sprengelii, had been left by the authors of 

 the "Synopsis Filicum," has studied some 1200 specimens of the group 

 and published a complete revision, in which are described 82 species, 

 based upon the following characters — nervature, outline of frond, 

 pubescence, texture, position of sori, etc. He supplies an analytical key 

 to render determination more easy. He gives full synonymy and distri- 

 bution of the species, critical notes, and often a figure. There are nine 

 new species, and some new varieties. In the appendix, two more new 

 species belonging to other groups are described. 



North American Ferns. — W. N. Clute % describes and figures 

 AspUnium Ferrissi, a new species collected in the canyon region of 

 Arizona by J. H. Ferriss. Other unique species have been recorded 

 from the canyon country which borders on Mexico. 



The same author § gives a simple account of the life-history of the 

 ferns, and describes a new extreme form, Nephrodiwn cristatum Clinto- 

 nianum f . silvaticum. 



He also || brings to an end his check-list of the North American 

 Fern worts. 



W. A. Terrylf describes a new pubescent variety of the ostrich fern, 

 transplanted from Plain ville into his own garden at Bristol (Conn.). 



A. Hans ** describes the result of hybridising the American species, 

 Polystichum acrostic ho ides with four forms of P. annulare. The latter 

 species is European, and not able to withstand the full rigour of the North 



* Bot. Zeit., lxvi. (1908) Abt. 1, pp. 25-87 (3 pis.). 



t Kgl. Danske Vid. Selsk. Skrift., ser. 7, Sci. iv., No. 4 (1907) pp. 247-336 

 (52 figs.). 



t Fern Bulletin, xvi. (1908) pp. 1-2. 



§ Tom. cit., pp. 5-13. || Tom. cit., pp. 16-23. 



U Tom. cit., pp. 3-5. ** Tom. cit., pp. 14-15. 



