Lichenes. — Pteridophjnen. 573 



C. Terricolous Lichens. 



The Vegetation of B. and C. is outlined but this is not very well 

 developed in the district. 



The paper concludes with a systematic list of the Howth Lichens, 

 and a Bibliography. There are three new species: Lecania atrynioi- 

 deSj Acarospora Benedarensis and Vernicaria Lorrain-Smühii. 



O. V. Darbishire (Bristol). 



Wheldon, J. A. and W. G. Travis. Lichens of Arran. 

 (Journ. Bot. LI. p. 248—253. 1913.) 



The authors enuraerate 119 species, but the}' confined their 

 own field work almost entirely to the coast, being prevented from 

 extending their field of Operations to the mountains. Their list 

 includes the lichens enumerated by Leightor and Crombie, and 

 additional unrecorded material collected by W. West. Some refe- 

 rence is made to the nature of the liehen substrata. 



0. V. Darbishire (Bristol). 



Kashyap-Shiv, R., The Structure and development of 

 the prothallus of Equisetum debile, Roxb. (Ann. Bot. XXVIII. 

 p. 163—181. 45 Textfig. 1914.) 



The author records that in some cases the result of germination 

 of the spores of Equisetum debile , Roxb., maj^ be a primary tubercle 

 from which the mature prothallus arises. In the older stage no traces 

 of the primary tubercle remain. The prothalli of this species are 

 radially symmetrical from the first and the constitute hemispherical 

 cushions, the lower half consisting of compact parenchymatous tis- 

 sue, the upper part of erect lobes; these are erect even when not 

 exposed to light. When exposed to direct light the prothallus is 

 red, owing to the possession of a pigment in addition to the Chlo- 

 rophyll; in a shaded position the prothallus is green, when it is 

 shaded in part and exposed in part both colours may be seen side 

 by side. The prothallus contains a fungus; the lower compact part 

 usually occupies a little less than half the height but in this matter 

 there is a good deal of variety. A well grown prothallus is 2 — 3 

 centimeters in diameter and 2 — 3 millimeters in height; it may bear 

 from one to fifteen plants-eight to ten being a not unusual num- 

 ber. There are no purely male prothalli, most prothalli seem to 

 bear archegonia onl}^ and a prothallus forming antheridia only pro- 

 duces them after its own archegonia have withered. The embedded 

 antheridia are developed from a superficial cell and are intermingled 

 with paraphyses. The archegonium has only one neck-canal cell, 

 while the other species of Equisetum have two. In the form of the 

 prothallus, the Single neck-canal cell, the structure of the antheridia 

 and the presence of paraphyses E. debile curionsl}?- recalls Lycopo- 

 dium cermium. The foot and root arise from the hj'pobasal part of 

 the embryo, stem and leaves from the epibasal part. The first leaf- 

 whorl usually has three members, but there may be two or four 

 as in other species. The first branch leaves a gap in the stele and 

 parenchyma passes into the middle of the latter. A little higher up 

 the main stele is a hoUow cylinder, which breaks up, further up 

 into separate bundles. 



Isabel Browne (University College, London). 



