1 6 INTRODUCTION. 



spores without elaters, and with the decay of the 

 surrounding tissues the spores are dispersed. 



In the Anthocerotece, the flat thallus, or frond, 

 consists of several layers of cells, and in this the 

 antheridia are immersed. When the antherozoids 

 are mature the apex of the cavity is ruptured, and 

 they escape. In a similar manner the archegonia 

 commence in the substance of the frond, and after 

 fertilization the spore-bearer or sporogonium elon- 

 gates, rising above the surface of the frond nearly 

 an inch, with somewhat the shape of a pod or 

 siliqua, which splits downwards into two valves 

 exposing the spores and a thin central columella. 

 The elaters extend from the columella to the wall 

 of the capsule, and when fully grown consist of a 

 row of three or four cells. 



This is but a brief summary of the principal 

 facts concerning reproduction in the Hepaticae, 

 which could not have been extended without 

 entering upon a long and specific account, such 

 as the space proscribed for this volume would not 

 permit. 



The combinations of male and female organs 

 are so complicated that they have originated the 

 following six terms, which it is necessary, simply 

 and briefly, to explain : 



Synoicous. When the male and female sexual 

 organs are intermixed in the same floral envelope. 



Paroicous. When with a hermaphrodite flower, 

 or a pure female flower, a definite shoot on the 

 same axis bears only antheridia. 



