CH. X] EMBRYO. 137 



and thus making a damp chamber in which a film of 

 water, coating its lower surface, may persist until the 

 antherozoids have swum to their destination. That the 

 antherozoid does reach the egg-cell is not a mere matter 

 of chance. The slime which fills the cavity of the canal 

 of the archegonium contains malic acid, and it has been 

 shown that the antherozoids are attracted by this acid. 

 If a capillary glass tube containing malic acid is introduced 

 into a drop of water in which antherozoids are swimming, 

 these organisms are found to direct their course towards 

 the tube and to force their way into the opening. In 

 the same way they force themselves into the slime in 

 the canal and ultimately make their way to the egg-cell, 

 which they fertilise. 



The fertilised egg-cell divides and subdivides and 

 grows into a complex of cells, an embryo or young plant. 

 This young plant is the sporophyte, the plant which will 

 bear sporangia, will produce spores and will thus com- 

 plete the cycle of development. It is not necessary to 

 give a complete account of the process of cell division 

 by which the embryo grows out of the egg-cell. It will 

 be enough to know that the first-formed cell-wall is more 

 or less parallel to the axis of the archegonium and divides 

 the egg-cell into an anterior and a posterior half. From 

 the anterior half the young stem and the first leaf are 

 developed, from the other half are formed the primary root 

 and a structure known as the foot. The foot has an 

 important function, for it is by means of it that the 

 embryo sporophyte is nourished in the early stages of 

 its existence. The prothallus has finished its share in 



