Mar. 1899.] BOTANICAL SOCIETY OF EDINBURGH . 185 



Stem the species varies greatly, intermediates between the 

 type and variety being frequent. In salt marshes fre- 

 quently submerged, the plant is most dwarfed, as are others 

 in the same situation. 



Garex rostrata, Stokes. — The leaves are narrow and much 

 channelled in marshes and shallow water, becoming broader 

 and flatter in deeper water. There is a form which grows 

 with the common plant that does not appear to depend 

 for its peculiarities on the surroundings. It is a more 

 robust plant, with the leaves broad and flat, or nearly so, 

 giving it a conspicuous appearance. Mr. Arthur Bennett 

 thinks it may be the form jjlanifolia, Norman, Fl. Arc. 

 Norivegia:. 



Hymcnophyllum Tunhridgcnse, Sm. — This species can be 

 known at sight from H. unilaterah by its broader fronds 

 spreading out horizontally, instead of being convex as in 

 the latter. It is also confined to damp shady rocks on 

 the low ground, while H. unilaterah frequently grows in 

 exposed places, and mounts to 2500 ft. altitude. 



Osmunda regalis, L. — Still to be found in many places, 

 but has been exterminated in some of its localities by 

 professional dealers. There is little danger of its com- 

 plete extinction, as it sometimes occurs on practically 

 inaccessible islands on the hill lochs. 



On Abnormal Conjugation in Spirogyra. 



By Pt. A. Eobertson, M.A., B.Sc. (With Plates.) 



(Read 9th March 1899.) 



Early in 1897 was commenced a series of experiments 

 on fresh-water alga?, to elucidate some points regarding the 

 sexuality of the group. These experiments are still in 

 progress. In the meantime there has appeared a very 

 exhaustive account, with a bibliography of the Conjugate 

 by W. and G. S. West, in "Annals of Botany" (March 

 1898). Some of the results which I obtained in experi- 

 mental laboratory cultures, particularly of Spirogyra, and 

 which I had regarded as pathological or induced, are there 



TRANS. BOX. SOC. EDIN. VOL. XXI. 



