HOFMEISTER, ON THE HIGHER CRYPTOGAMIA.. 319 



The central cell divides into two (PL XLIV, fig. 4), 

 and each of the cells thus formed divides repeatedly 

 into two cells turned towards all three directions of space. 

 The cells of the two enveloping layers meanwhile divide only 

 by septa perpendicular to the outer surface. The sporan- 

 gium thus becomes a globular mass of large cells enclosed 

 by a double layer of smaller tubular cells, and borne upon 

 a very short cylindrical stem. The larger cells — the 

 mother-cells of the spores — isolate themselves during the 

 further growth of the fruit ; the cells of the inner layer of 

 the covering produce in the mean time numerous free small 

 cells in their interior, which, as the membranes of their 

 mother-cells divide, escape from the latter into the inner 

 cavity of the sporangium (PL XLIV, fig. 5) ■ at a later 

 period they are absorbed. Each spore-mother-cell when it 

 has become free divides contemporaneously into four 

 daughter-cells which are the special mother-cells of the 

 spores. This stage of development is attained at an earlier 

 period by the lower sporangia than by the upper ones. 

 After the walls of the special mother-cells have increased 

 considerably in thickness, a spore is produced in each of 

 them (PL XLIV, figs. 6, 10, 11). Up to this point all 

 the sporangia behave alike. From this time however the 

 further development of the lowermost sporangium of each 

 compartment of the fruit differs very materially from that 

 of the others. In the sporangium in question the special 

 mother-cells and spore- cells (which are arranged in sets of 

 four) all die slowly off except one (or two). The spores of 

 the one set which remains soon become free by the absorp- 

 tion of the walls of the mother-and special-mother-cells, and 

 assume a globular form. At first all four increase rapidly 

 in size (PL XLIV, fig. 7); their walls then become much 

 thickened but unequal-sided, so that the globular inner 

 cavity of the young spore becomes excentric (PL XLIV, 

 figs. 6, 11). The growth of one of the spores soon exceeds 

 that of the others. The former alone continues to develope 

 itself, whilst the growth of the others is arrested, and being- 

 pushed aside — like the . remains of the mass of special 

 mother-cells — by the one growing spore, they are soon dis- 

 solved. When the fruit is ripe the large spore occupies the 



