Cavers: A'o/cs on Yorkshire BryopJiyles. 



443 



bray, Co. Wicklow, and in specimens from Yorkshire, of quite 

 different habit, which Mr. W. H. Pearson tells us agree with 

 Gottsche's Morckia liibernica, we have found the tissue of the 

 midrib quite homog-eneous without any trace of an axial strand. 

 In another plant, however, kindly sent us by Mr. David McArdle, 

 of the Royal Glasnevin Botanic Gardens, from sandy flats at 

 Malahide, Co. Dublin, under the same name, but which he 

 places under var. Wilsoniana Carrington, we find two distinct 

 lateral strands in the midrib, each consisting-, in transverse 

 section, of about twentv cells, which do not differ from the 



Fig. 2. —Part of Fig. i., II., >; 70. 



surrounding tissue in width or in the thickness oi their walls. 

 These walls, however, are distinctly brown in the unstained 

 condition, and hold aniline stains more strong-ly than the sur- 

 roundings tissue. On long-itudinal section many of the strand- 

 cells do not differ greatly from the neighbouring cells, but they 

 tend to be longer, and some are of considerably greater length. 

 In the absence of living material on which to experi- 

 ment we regard these strands as very primitive water-conducting 

 channels.' In all the Coatham plants of which sections were 

 examined, the midrib showed two lateral strands, corresponding 

 in position with the strands described by Mr. Tansley in the 

 Malahide specimens. In the Coatham plants, each strand 



1903 November i. 



