70 HOFMEISTEB, ON 



an active multiplication in the direction of their growth 

 (outwards and at the same time obliquely upwards) of the 

 peripheral layers of cellular tissue of the apex of the stem. 

 This multiplication extends downwards from the rudiments 

 of the perianth to the second or third pair of leaves. By 

 this process the end of the stem which bears the archegonia 

 becomes depressed below the level of an annular wall- 

 shaped enlargement of the cortex of the stem, which 

 enlargement bears upon its upper margin the young 

 perianth, and upon its outer surface the uppermost pair of 

 stem-leaves. An expansion of the cells of the above 

 enlargement, in a direction parallel to the longitudinal 

 axis of the stem, ultimately raises the points of insertion of 

 the upper leaves above the apex of the calyptra. 



From an exaggeration of the same condition is produced 

 the peculiar formation of the (abnormal) perianth of Calypo- 

 c/eia Trichomanes. Gottsche has shown* that the short 

 few-leaved branch which springs laterally from the median 

 line of an inferior leaf, bears upon its apex the archegonia 

 which are immediately surrounded by the last leaves ; the 

 apex of this branch inclines upwards, and becomes a round 

 fleshy knob.f Successful longitudinal sections perpendicular 

 to the plane in which the surfaces of the leaves of the prin- 

 cipal axis lie, and passing through this axis, and also through 

 the young fruit-branch which lies laterally in the axil of one 

 of its inferior leaves, proved to me that the latter branch, 

 which at first is directed obliquely downwards, curves itself 

 upwards, so that at the period of impregnation the arche- 

 gonia are erect (PI. X, fig. 1). The central cell before 

 impregnation is exceedingly small. The completion of the 

 impregnation is first recognisable by an unusually active 

 multiplication of the cells of the central portion of the 

 archegonium during its conversion into the calyptra ; a 

 multiplication which forthwith commences in the tissue of 

 the fruit-branch immediately adjoining the base of the 

 archegonium (PI. X, fig. 1). The small-celled tissue thus 

 formed, which bears the impregnated and the abortive 

 archegonia, becomes developed into the fruit-sac. The 



* ( Nova Acta Ac. C. L.,' xxi, p. 427. 

 f L.c, p. 438. 



