90 MARCHANTIA POLYMORPHA. 



6. The elaters, elongated cells, with spiral thickenings. Re- 

 move the cover-slip and allow the crushed specimen to 

 become dry as you watch it, and observe: 



7. The behavior of the elaters. 



8. Draw. 



ANNOTATIONS. 



From a morphological point of view Marchantia is a plant 

 of unusual interest, on account of its remarkable degree 

 of differentiation. The upper part of the prostrate game- 

 tophyte has differentiated highly specialized tissues for 

 chlorophyll work, the whole upper surface being divided 

 into air-chambers in which we find chlorophyllose cells, 

 that show a striking resemblance to the green Algae. This 

 air-chamber is open to the exterior by a pore whose 

 edge is formed by four layers of cells. The lower part 

 of the body is differentiated for the work of support 

 and storage of foods, and must also transfer materials 

 from the ventral surface up to the chlorophyll tissue. 



As the gametophytes grow they branch dichotomously, 

 the older parts steadily dying away, thus giving rise to 

 separate plants. Vegetative reproduction is also carried 

 on freely by means of gemmae, designed especially for 

 the purpose, and borne in special organs. The plant is 

 extremely successful in its vegetative reproduction. 



The sexual reproduction also shows an advance over 

 Riccia. Special branches bear the sexual organs, the 

 sexual organs themselves being more complex than 

 in Riccia; furthermore, one plant bears but one kind of 

 sex organ, i.e., the species is dioecious. 



Fertilization takes place within the venter of the 

 archegonium, and the oospore germinates in the same 



