452 



Cavers : Notes on Yorkshire Bryophytes. 



tion of tissues adapted for the conduction and storage of water, 

 such as would be the case when g-rowing- on sandy soil and 

 exposed to periods of drought. The writer has observed 

 analogous modifications in the internal structure of other thal- 

 loid Hepaticaj which had been cultivated indoors in the same 

 manner. In Fegatella conica the large mucilage-sacs normally 

 present in the midrib are poorly developed or absent in plants 

 grown under cover and kept constantly moist. In the case of 

 Preissia commiitata the dark-coloured and thick-walled fibres 

 which are so characteristic of the plant in its natural habitat 

 were found to be absent from the midrib of the new branches 

 produced under cultivation in moist surroundings. 



The antheridia and archegonia are borne on separate plants, 

 which scarcely difi"er in other respects. In the male plant 



Fig. 4. — Transverse (I.) and longitudinal (II.) sections of a male plant, showing the antheridia 

 An.) and the scales (S.) covering them ; Rh,, rhizoids. I. X 25, II. X 70. 



(Plate, I.) the antheridia are produced in large numbers on 

 the upper surface of the midrib. Each antheridium is nearly 

 spherical, with a short stalk, and is covered by a scale which 

 arises immediately behind it and grows forwards like a hood 

 (Fig. 4). These scales have their free margins cut up into 

 irregular pointed lobes, and sometimes several of them grow 

 together, as in Petalophyllum, so as to form a network of 

 chambers, each occupied by an antheridium. The antheridia 

 are usually accompanied by mucilage-hairs (paraphyses), each 

 consisting of a single row of cells. 



Naturalist, 



