238 Plagiochasma apPendiculatum and P. articulatum 
androecium is quite terminal at first. The three considerations 
are:—(1). The arrangment of the scales at the tip of the lobes 
which is very similar to that at the tip of the vegetative lobe. 
(2). The repeated branching of the receptacle, two or three times in 
some specimens. (3). The invariably acropetal succession of the 
antheridia in all lobes exactly as in Marchantia, the highest genus 
of the Marchantiales. 
