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XVIII. 



CALLOSITIES OF NITOPHYLLUM VERSICOLOR, HAEV, 

 (A New Mode of Vegetative Eepeoduction op Floeide^). By 

 T. JOHNSON, D. Sc, F.L.S., Professor of Botany in the Eoyal 

 College of Science, Dublin. (Plate XIV.) 



[Eead November 18, 1891.] 



Nit op III/ Hum versicolor, Harv., is one of the rarest of the ten' 

 species of the genus Nitophyllum, Grrev., known to occur on the coasts 

 of the United Kingdom. Harvey^ says of it : *' Yery rare ; thrown 

 up prohably from deep water; annual; June to August; Ilfracombe, 

 Miss Hill (1800) and Mrs. Griffiths. Youghal ; Miss Ball (1834) ." 

 The plant occurs on the coast of France, and is said by J. G. 

 Agardh^ to be found " In Atlantico ad littus Europae tem- 

 peratae." 



W. versicolor, Harv., is characterized by a change of colour from 

 rosy red in salt to golden orange in fresh water, but more espe- 

 cially by the presence of peculiar swellings described by Harvey as 

 " ciliiferous calli " (PI. xiv, fig. 1 c). These callosities occur as 

 thickenings on the tips and lateral margins of the frond. From their 

 outer edge cellular, simple, or branched filaments project. From 

 the cells of the callosity, when cut open, Harvey found minute 

 granules escape in great abundance, bearing " no resemblance to 

 spores of any description." Harvey further stated that the fructi- 

 fication of iV. versicolor, Harv., was unknown, unless the swellings 

 were of the nature of fruits. Greville,* writing of the callosities, 

 says : "A curious appearance of what might be called pseud-fruc- 

 tification has been detected upon Belesseria Bonnemaisoni [N. versi- 



1 E. M. Holmes, and E. A. L. Batters : " Eevised List of the Britisli Marine Algae," 

 in Annals of Botany, v. 1890. 



2 W. H. Harvey : Phyc. Brit. PI. ix. 



3 J. G. Agardh : Sp. Alg. in., p. 471. 



* E. K. GreviUe: "Crypt. Flora," Vol. vi., PL cccxxii. 



