322 Durand : Marchantia polymorpha 



the end a feeling of satisfaction in having acquired a fairly compre- 

 hensive knowledge of the embryology of that species and of the 

 group to which it belongs. Moreover, the preparation of such 

 sets may prove to be of almost as much value to the teacher as to 

 the student. 



As the representative of the Marchantiaceae the writer natur- 

 ally selected Marchantia polymorplia, it being the most accessible 

 as well as the most easily studied member of the group. An 

 examination of what has been written concerning this species 

 brought out a rather surprising state of affairs. Marchantia poly- 

 morpha has long been a favorite object for class study. It has 

 been described and illustrated in practically every textbook treat- 

 ing of the liverworts, and has been made the subject of numerous 

 investigations, so that it would seem as if nothing remained to be 

 done with it. Yet nowhere has there ever been published an 

 even approximately complete account of the development of the 

 antheridia, archegonia, and sporogonia of this species, nor any- 

 thing approaching a complete series of figures illustrating these 

 phenomena. 



Inasmuch as this plant is so commonly used in class work it 

 has seemed to the writer to be desirable that a fairly complete 

 series of illustrations should be available for the use of students. 

 The accompanying figures with the brief account of the develop- 

 ment of the sexual organs and sporogonium are therefore presen 

 in the hope that they may be found useful. 



Marchantia grows commonly on damp soil in ravines or along 

 wood-roads, but reaches its best development on damp, burnt soil. 

 The writer once visited a burnt-out swamp several acres in extent 

 in which the ground was nearly completely covered with luxuriant 

 thalli to a depth in some places of several inches. The gameto- 

 phores begin to appear early in May, and the sporogonia mature 

 in July. 



Antheridium 

 The antheridia of Marchantia are sunk in cavities in the upp« r 

 surface of the antheridiophore. They develop in acropetal suc- 

 cession, the youngest being near the margin and the oldest near 

 the center of the disk. They do not originate from all portions o\ 

 the margin equally but the younger ones are produced in certain 



ted 



