1894. ADAPTATION IN LIVERWORTS. 197 



in the thallose forms, developed immediately behind tlie apical cell, 

 are well known. It is now known that similar papillae are commonly 

 formed at the apex of the very young leaf in the foliose forms, and 

 hang over the apical cell. This uses up the apex of the leaf, and the 

 main part of this organ is subsequently formed by intercalary growth. 

 The papillae usually occur singly or in a pair on each leaf ; but in 

 Physiotiiim ^iganteum there are three to each upper lobe, which hang 

 over the stem apex, so that the leaf in this state presents an appear- 

 ance irresistibly recalling the jester's cap and bells. 



REFERENCES. 



1. Goebel, K. — " Archegoniatenstudien," Flora, Dec, 1893. 



2. Reeves, J. — " On the Development of the Stem and Leaves of Physiotium 



gigantcum," Journ. of Botany, Feb., 1894. 



Jesse Reeves. 



