466 APPENDIX. 



prothallus is an independent plant. By means of its chloro- 

 phyll it can assimilate the carbon dioxide of the atmosphere, 

 and by the aid of its root-hairs it absorbs water and salts 

 from the soil. Owing to its thinness, gases can penetrate to 

 all parts, hence no stomates are required. The upper surface 

 of the prothallus is quite smooth, but on the lower surface 

 there are, besides the root-hairs, two kinds of projecting 

 bodies, in which are formed the germ-cells. These bodies can 

 be seen with a lens, or with a low power of the microscope. 



'-RHIZOID ARCHEGONIA 



APICAL CELL 



ANTHERIDIA 



RHIZOIDS 

 Fig. 6. Germination of Spore and Development of Prothallus of- Fern. 



At the front of a well-grown prothallus, just behind the 

 notch, there are several little finger-like projections, situated 

 on the cushion ; these can be seen on washing the soil from 

 the underside and holding the prothallus up to the light. 

 These are the archegonia, or egg-producing organs. Each 

 archegonium is a minute flask of which only the neck projects 

 from the surface, pointing backwards towards the pointed 

 hinder part of the prothallus. The base of tha flask is 

 embedded in the tissue of the cushion, and contains the egg- 

 cell. Behind the archegonia there are numerous smaller 

 bodies, scattered over the whole underside of the prothallus ; 

 these are spherical bodies, called antheridia, in which the 

 male germ-cells, called antherozoids, are produced. 



In examining with the microscope a prothallus mounted in 

 water the underside being placed upwards one may see an 

 antheridiuin burst and set free the male cells. These are 



