t 



620 Graham: Conocephalum conicum 



but in an additional covering or sheath which Hes outside of the 

 calyptra and is derived from the adjacent tissue of the gametophore. 

 This outer sheath does not seem to have been described by any 

 writer on ConocepJiahim, although it was figured in outhne by 

 Bolleter {Joe. cit. 364, /. A). This writer makes no reference to 

 this feature, either in the text or in the explanation of his figure. 

 Since no similar organ seems to have been described for any of the 

 other Marchantiaceae, its origin and development will now be con- 

 sidered in detail. 



As already pointed out in a previous paragraph, the archegon- 

 ium of Conocephalum coniaini is developed in a flask-shaped cavity 

 in the tissue on the under side of the gametophore {figure jy, j8). 

 The gametophore of this plant, in common with all other Mar- 

 chantiaceae, possesses numerous large air-chambers separated by 

 plates of cells. The chambers in the upper part of the gameto- 

 phore are large and nearly isodiametric. Toward the lateral 

 margin they become smaller and the smallest ones are at the base. 

 The tissue making up the wall of the archegonial cavity on the side 

 toward the stalk of the gametophore is solid at the time of fertili- 

 zation {figure J f), but after this time air-chambers appear in this 

 also {figure j8). In the vicinity of the archegonial depression 

 these chambers are long, narrow, and compressed, so that they 

 appear much more slender in longitudinal section than those in the 



w 



upper part of the gametophore. 



At the time of fertilization the archegonial cavity opens to the 

 outside. Through this opening the neck of the archegonium pro- 

 trudes as has already been stated {figure jf). After fertilization 

 the neck of the archegonium withers and turns brown {figures j 4, 

 jS, 4.0), as is usual in the bryophytes. Then the lip-cells form- 

 ing the margin of the opening of the archegonial cavity elongate 

 transversely and grow until those on opposite sides meet and the 

 opening is nearly or quite closed {figures 40, 44, 45, 52). As a 

 result of this growth the archegonium with its embryo is contained 

 in a closed cavity. 



As the embryo and the calyptra enlarge, the tissue of the 

 gametophore bounding the archegonial cavity on the side adjacent 

 to the stalk of the gametophore elongates rapidly in a vertical 

 direction and since little or no growth takes place on the opposite 



