CHAPTER X. 



PILULARIA GLOBULIFERA AND MINUTA ; MARS1LEA 



PUBESCENS. 



The fruit of Pilularia is the transformed end of a furcate 

 branch, which is apparently produced in the axil situated 

 between one of the long thin fronds and the" principal axis, 

 and which in Pilularia minuta is usually a lateral bud 

 situated in one of the normal bifurcations of the stem. In 

 P. minuta it forms when in the very young state, a globular 

 mass of delicate homogeneous cellular tissue flattened at the 

 apex. An outer layer of cellular tissue, composed of four 

 layers of cells, surrounds two lenticular cavities which are 

 separated from one another by a thick septum. The inner 

 side of the outer wall bears the rudiments of sporangia. In 

 this species, even at this early period of development, no 

 traces of the junction of the amalgamated parts are visible 

 at the apex of the fruit (PI. XLIV, fig. 8). In the young 

 fruit of Pilularia globulifera the commissures of the four 

 delicate cross septa of the divided chambers exhibit very 

 manifest lines of junction, which, in the half developed fruit 

 (upon the outer wall of which numerous hairs are formed) 

 are still unclosed. Here also clavate masses of cellular 

 tissue, the first rudiments of the sporangia, spring out of 

 the inner wall of the outer surfaces of these chambers. In 

 Pilularia minuta there are only two or three of these masses, 

 in other species as many as eight vertically one over the 

 other. The wider end of the very young sporangia, which 

 is borne by a short thick stem, exhibits a large central cell 

 surrounded by a double layer of smaller cells (PI. XLIV, fig. 3). 



