200 HOFMEISTER, ON 



the septum in the hinder cell is inclined downwards and 

 backwards, that in the front cell upwards and forwards. 

 The young embryo now consists of four cells, having the 

 form of segments of a sphere, which fall into a vertical 

 plane passing through the longitudinal axis of the pro- 

 thallium (PI. XXVIII, fig. 1). Pteris aquilina and Aspidium 

 jilLv-mass exhibit a specific difference in the angles of incli- 

 nation of the newly-formed septa. The upper angle which 

 the newly-formed septum in the front cell forms with the 

 older one (PI. XXVI, figs. 6 \ 7 \ h, c) is widely open in 

 Asjjidium filix-mas ; it is almost a right angle; the lower 

 angle of the septum in the hinder cell is very acute (PI. 

 XXVI, figs. 6 \ 7 \ a, d). In Pteris aquilina this state 

 of things is exactly reversed (PL XXVIII, figs. 1 \ 3 \ a, d, 

 b, c). In connexion with this difference there exists also a 

 difference in the further development. In both species the 

 stem-bud and the first frond are formed out of one of the 

 four cells, viz., the lower one of the two front cells (PL 

 XXVIII, figs. 1, 3, a.c; PL XXVI, figs. 6, 7, a.c), and 

 the first root is produced from another of those four 

 cells. But in Aspidium filix-mas the mother-cell of the 

 root (b,d PL XXVI, figs. 6, 7) lies opposite to that 

 of the stem ; in Pteris aquilina it lies at the side (a,d 

 PL XXVIII, figs. 1, 3). In Aspidium the primary 

 abortive axis of the embiyo,* is developed almost ex- 

 clusively by continual divisions of that one of the four 

 cells which is most distant from the mouth of the archego- 

 nium. In Pteris the descendants of the two cells which 

 are furthest from the archegonium compose this organ, 

 which in that genus is much larger (PL XXVIII, fig. 3). 

 The fourth cell of the young embryo which lies under the 

 mouth of the archegonium multiplies still further in Aspi- 

 dium, although only to a slight extent. Its derivative 

 cells do not form a detached portion of the germ-plant, 

 but go to form the cortical portion between the back of 

 the first frond and the first root (PL XXVI, fig. 7). 



All the vascular cryptograms in which the germination 



* The foot-like appendage by which the young fern is attached to the pro- 

 thallium. Only a few of the cells of the rudiment of the root take part in the 

 formation of this "foot" (PL XXVI, fig. 7). 



