280 



FOUNDATIONS OF BOTANY 



Do both occur on the same thallus ? On what part of the thallus 

 do they occur, and do they differ in this respect ? 



340. Antheridia. The antheridia are formed as outgrowths 

 from the upper surface of the crenate receptacle, but by further 

 growth of the receptacle they become imbedded. They should be 

 examined under a high power and sketched in outline. The anther- 

 idium produces numerous motile antherozoids, each with two cilia. 



341. Archegonia and Sporophytes. The receptacle with recurved 

 rays bears the archegonia. Note whether they occur above or below 

 and in what relation to the rays. How are the archegonia protected ? 



Note the cells which surround 

 the central canal and form the 

 elongated neck of the archego- 

 nium. Does the archegonium 

 open upward or downward ? At 

 the base look for the germ-cell. 



The antherozoids enter the 

 central canal and penetrating 

 to the egg-cell fertilize it, after 

 which it begins to divide and 

 grows into a sporophyte. In the 

 older specimens, therefore, the 

 sporophytes will be found more 

 or less developed. The archegonium remains upon the tip of the 

 sporophytes. The mature sporophyte contains the spores and also 

 peculiar elongated tapering threads with spiral thickenings. These 

 are called elaters. 



342. Hepaticae. Marchantia represents only a small 

 division of the Hepaticce, and is not typical of the larger 

 number of species. In spite of this it is chosen for study, 

 because it is widely distributed and more available for 

 study than most others. In most species the fruit lasts 

 but a little while and good material is hard to obtain. In 

 Marchantia the fruiting organs are abundant, more gradual 

 in their development, and more persistent. Marchantia and 



FIG. 205. Sectional View of Female 

 Receptacle of Marchantia. (x 5.) 



