441 



NOTES ON YORKSHIRE BRYOPHYTES. 



II. PALLAVICINIA FLOTOWIANA. 



F. CAVERS, B.Sc. 



The hepatic from Coatham Marshes which is described in the 

 present note, and for numerous dried and fresh specimens of 

 which I am indebted to the kindness of Mr. W. Ing^ham, is 

 a Pallavicinia (sub-genus Morckia). It ag-rees closely with 

 P. Flotoioiana (Nees) Schiffn. (syn. P. Hibcrnica Hook. var. 

 Wihoniana Carr. ), but the following description, based on the 

 writer's examination of a large number of plants, will be found 

 to differ in some points from those given by Schiffner* and 

 Warnstorf.f The plants grow in crowded patches on sandy 

 soil. Each plant (Plate, I. -III.) is from lo to nearly 30 mm. 

 long and 3 to 5 mm. broad. The shoot or thallus branches 

 dichotomously, but the forking takes place relatively seldom, 

 usually once or twice only. There is a broad midrib, the 

 posterior portion of which is bare* and cylindrical, and which 

 bears on its lower surface numerous whitish rhizoids. Anteriorly, 

 the midrib bears on either side a broad thin wing which is 

 sharply curved upwards at the margin and is thrown into 

 numerous folds. This folding, which is usually fairly regular 

 and gives the plant a neat, crisped appearance, is simply due to 

 the more active growth of tlie marginal region of the wing ; the 

 margin itself usually remains entire, but is sometimes slightly 

 lobed. 



At the apex of each branch of the thallus there is a deep 

 notch, the bottom of which is occupied by the growing point, 

 consisting of a short transverse row of wedge-shaped initial- 

 cells. From the ventral surface, immediately behind the row of 

 initial-cells, there arise numerous filaments, each consisting of a 

 single or partly double series of cells and ending in a club- 

 shaped mucilage-cell, which curves upwards over the growing- 

 point. 



The posterior portion of the thallus, consisting of the cylin- 

 drical midrib, is roughly oval in cross-section, the dorsal surface 

 being flattened and the ventral rounded. The midrib is from 15 

 to 20 cells in thickness, and on tracing forwards a series of 



* SchifFner, V., ' Untersuchutig-en iiber Morckia Flotoiinana und iiber das 

 \'erhaltniss der Gattungen MiJrckia uiid Calycularia zu einander.' CEsterr. 

 Bot. Zeitschrift, 1901. 



t Warnstorf, C, ' Moose ' in ' Kryptog-amenflora der Mark Branden- 

 burg-,' p. 99. 

 190.-; November i. 



