lO INTRODUCTION. 



process is more elaborate and can be studied 

 readily in MarcJiantia. Cup-like bodies, seated upon 

 the fronds and exposed to the light, will be seen 

 to contain minute rounded greenish granules, like 

 eggs in a miniature bird's nest. These little granules 

 are the swollen apical cells of the slender filaments 

 which have grown from the bottom, and they ulti- 

 mately fall out as gemmae. On reaching the 

 ground, or other substratum, they germinate and 

 become young plants. 



Reproduction. 



The reproductive process and organs vary not 

 only in the different orders but to a certain extent 

 in the different genera ; it will, nevertheless, be 

 possible to furnish such general information as may 

 assist in the comprehension of particular phenomena 

 as they may arise. The foliose Jungermanniae will 

 serve as the best illustration for this purpose, and 

 here the reproductive organs generally occupy the 

 end of the primary axis, or special lateral branches. 

 It will be found in most cases that the ordinary 

 cauline leaves increase in size gradually towards 

 the apex. Almost as gradually, in fertile shoots, 

 do they merge into the enlarged and modified leaves, 

 which constitute the involucre, or pcricJuctium, of the 

 fruit-bearing receptacle. These involucral bracts, or 

 perichaetial leaves, vary in size and number as well 

 as in form, and may be either free or connate at the 

 base, more or less embracing the perianth or colesule 

 ''sometimes inaccurately termed the calyx) enclosing 



