Cavers : Notes on Yorkshire Bryophytes. 



247 



receptacle, the stalk is extremely short, and no tuberculate 

 rhizoids have been developed on the receptacle. Evidently, 

 therefore, the apical g-rowth of the branch remains in abeyance 

 during- the early development of the receptacle. If fertilisation 

 occurs in one or more of the archegonia this g-rowth is arrested, 

 because then the growing--point is used up in the formation of 

 the receptacle-stalk. The receptacle grows in size, numerous 

 rhizoids are developed, and the compact tissue in the receptacle, 



Fig. 6. — A. — Part of Fig-. 5, C, x 90, showing- on the left the receptacle stalk with its ventral 

 rhizoid bearing groove, on the right one of the lobes (involucres) with a sporogonium 

 enclosed in the cah'ptra. The outer portion of the lobe shows air-chambers, opening by 

 large barrel-shaped pores, the inner portion consists of compact starch-bearing tissue. 

 Between the stalk and the involucre are shown the narrow scales in cross-section. B. — 

 Longitudinal section of a youn^- sporogonium, with its calyptra. In the upper portion 

 (capsule) of the sporogonium the archesporial tissue is shaded. X90. C. — Upper portion 

 of a nearly ripe capsule in longitudinal section, showing the lens-shaped apical cap and 

 some of the spores and elaters. X 120. D. — Spore in surface view, from the inner side, 

 showing the three radiating ridges. The surface is covered with a network of smaller 

 ridges. X 200. E. — Spore in section, showing the thin endospore, the exospore (shaded), 

 and the thick outer coat (epispore) with its ridges. X 200. 



1904 August I. 



