326 HOFMEISTER, ON 



passage leads through this gelatinous mass to the pro- 

 truding portion of the inner spore-membrane. At the base 

 of this passage are found the debris of the three sister- 

 cells, which were produced in the same mother-cell with the 

 spore. These are small shrivelled tetrahedral cells, which 

 are attached by one of their points to the wart-like protru- 

 sion of the inner layer of the outer membrane of the spore 

 (PL XLIV, %. 16). 



The inner cavity of the spore is filled with a fluid con- 

 sisting of albuminous matter and yellow oil, and containing 

 numerous large and small starch granules. The larger 

 granules exhibit manifest lamination, and sometimes also 

 indications of twin-granules. The protruding portion of the 

 apex of the spore is separated from the rest of the cavity of 

 the spore by a very delicate septum. It forms a distinct 

 cell filled with a finely granular mucilage. When treated 

 with caustic potash it exhibits in its middle point a nucleus 

 of an ellipsoid shape (PL XLIV, fig. 18). This cell is the 

 mother-cell of the prothallium. 



Germination begins a few hours after the escape of the 

 spore from the opening fruit. In the primary cell of the 

 prothallium two new nuclei appear in the place of the pri- 

 mary nucleus which disappears (PI. XLIV, fig. 17), and 

 shortly afterwards the cell is divided into two longitudinal 

 halves by a vertical septum. The longitudinal division is 

 repeated in each half by a septum at right angles to the 

 former one (PL XLIV, fig. 19). In the mean time an 

 orange-red colouring matter appears in the mucilaginous 

 fluid contents of the two or the four cells, in the form of 

 small vesicles (or drops ?) By a series of bipartitions the 

 prothallium is transformed into a hemispherical cellular 

 mass (PL XLIV, figs. 20 — 24), consisting of a central cell 

 with mucilaginous contents, supported upon a double layer 

 surrounded by a triple layer of narrow cells. The four 

 longitudinal rows of cells which extend beyond the apex of 

 the central cell, part asunder at then* edges of contact, and 

 an open narrow passage leading to that cell is formed (PL 

 XLIV, fig. 22). 



The structure of the prothallium of Marsilea consequently 

 agrees in its essential features with that of Pilularia, except 



