Cavers :' A'o/cs 0)1 Yorkshire Bryopkyies. 333 



(Fig-. 4, I., IV.) the cells in this region are seen to be densely 

 filled with granular contents, giving- the reactions of oil and of 

 proteid matter, but not of starch. The outer layers of the stem 

 form a sheath or envelope to the tuber, two or three cells in 

 thickness ; these cells are flattened and are usually almost 

 empty, but sometimes contain fungal hyphai, which may pass 

 inwards and ramify throug-h the densely granular cells of the 

 tuber. Later in the year, the more delicate parts (leaves, etc.) 

 become withered and discoloured and ultimately disappear, but 

 the tuber remains intact and afterwards grows out to forn-j 

 a new plant, giving- rise to a cylindrical process which passes 

 over into the normal leafy shoot. 



The sexual organs and the sporogonium of Petalophyllum 

 ao-ree closely with those oi Fossoiubronia. In the male plant the 

 antheridia are scattered along the upper surface of the midrib ; 

 in the female plant the archegonia occur in groups on the 

 lateral wings of the stem, standing between the leaves. The 

 antheridium is nearly spherical and is borne on a short stalk ; it 

 is covered by a scale which may be either hood-like, growing 

 forwards over the antheridium, or tubular, growing up around 

 the antheridium as a sheath. Frequently, as noted by Leitgeb, 

 the sheaths or scales of adjacent antheridia grow up together so 

 as to form a network of chambers, each containing a single 

 antheridium. Each female plant bears several groups of arche- 

 gonia, standing one behind another and on both sides of the 

 midrib. According to Leitgeb each group may contain as many 

 as twelve archegonia, but I have never found more than eight, 

 whilst most of the groups examined contain only five or six of 

 these organs. Each group is at first surrounded by a number 

 of narrow scales or leaf-like outgrowths from the stem-surface. 

 Should one or more of the archegonia be fertilised the perianth 

 begins to grow up as a tubular sheath which surrounds the 

 whole group of archegonia and lies immediately within the ring- 

 of scales. As the perianth grows upwards some of the scales 

 (involucral leaves, female bracts) are carried up on its outer 

 surface, so that the mature perianth bears externally a number 

 of leaf-like appendages. Between the archegonia there grow 

 out numerous club-shaped hairs which secrete mucilage. 



The large spherical capsule is borne on a well-developed 

 stalk which ends below in a conical swelling or foot ; the 

 margins of the foot grow upwards round the base of the seta, 

 so as to be heart-shaped in longitudinal section, as in Pellia. 

 When the capsule is mature the seta becomes elongated and 



1903 September i. 



