INTRODUCTION. Xlll 



fertile organs. Besides the specialised leaves or bracts they are 

 usually surrounded by numerous, hyaline, jointed hairs, called 

 paraphyses. The leaves composing the fertile flower are called 

 the perichsetial leaves or bracts ; those surrounding the antheridia, 

 when these are separate from the archegonia, are termed the 

 perigonial leaves or bracts. These bracts, of either kind, are 

 often highly differentiated, and important to observe; but in many 

 groups of mosses they are hardly distinct from the ordinary leaves. 



The antheridia (Tab. V. 18) are small elliptic or clavate 

 bodies, usually of a thin, loosely areolated texture and pale 

 brownish colour, more or less wide and obtuse at the apex; they 

 contain the antherozoids which, escaping, enter the archegonia 

 and fertilise the oosphere, the cell which ultimately developes into 

 the mature fruit. 



The archegonia (Tab. V. 19) are narrower in shape, resemb- 

 ling a narrow, long-necked bottle, and are almost always of 

 a deep red colour ; they usually occur in some numbers in each 

 perichaetium, but it is as a rule only one which is fertilised and 

 produces fruit. 



The relative position of the antheridia and the archegonia is 

 of great importance, and different terms are applied to the in- 

 florescence in accordance with these different relationships ; as 

 they are somewhat difficult to grasp these terms are here tabulated. 



The antheridia and archegonia may occur only on separate 

 plants; the inflorescence is then termed dioicous (Tab. V. 20 & 21). 



If they occur on the same plant it is termed monoicous. This 

 includes several distinct forms, according to the positions of the 

 two organs ; they may occupy two different positions on separate 

 parts of the stem, the antheridia then being usually enclosed in 

 distinct perigonial bracts ; the inflorescence is then said to be 

 autoicous (Tab. XVII. E. 10). 



Or the antheridia and archegonia may be mixed together in 

 the same flower, which is then termed synoicous (Tab. V. 22). 



Or, finally, the antheridia may be placed just below the fertile 

 flower, without special perigonial bracts, simply in the axils of 

 the lower perichffitial bracts ; this form of inflorescence is termed 

 paroicous (Tab. V. 23). 



Occasionally two of these forms of inflorescence are found 

 side by side in the same species. 



It may be mentioned that the paroicous form of inflorescence 

 appears to be confined to Acrocarpous mosses, and the synoicous 



