FEEN 335 



and a body, in which may be distinguished an 

 oosphere. Study the structure of these parts 

 and compare with the corresponding parts of 

 Marchantia. Draw. 



PHYSIOLOGY 



a. The germination of the spore and the development of 

 the prothallium. 



Sow a few spores in a drop of water in a moist 

 chamber. How long before the spore ruptures? 

 What changes take place in it at this time ? "What 

 is the shape of the embryo prothallium? How 

 long before the primary root-hairs develop ? Only 

 the first stages can be observed in water cultures. 

 To get the later developmental stages, spores may 

 be sown on slabs of plaster of Paris, pieces of 

 porous earthenware, or, best of all, on clean, damp 

 sand. The cultures must be kept damp and be 

 examined every few days. On older prothallia, 

 look for the first rudiments of the asexual gen- 

 eration (the fern-plant proper), which in sections 

 will be seen issuing from an archegonium which 

 has been fertilized. Still later stages will show 

 a single leaf borne above the prothallium, and 

 from this point the development may be watched 

 with the naked eye. 



