THE HIGHER CRYPTOGAMTA. 71 



larger wide-celled moiety of the fruit-stalk above the former 

 takes no part in this new formation. An active cell- 

 multiplication continues to take place in the former tissue 

 for a long time. In the cells undergoing division, transverse 

 septa perpendicular to the convex outer surface of the fruit 

 branch often make their appearance. The annular zone of 

 new cells thus formed, which lies at the greatest distance 

 from the archegonia, undergoes, immediately after its forma- 

 tion, a considerable longitudinal elongation, at right angles 

 to the partition-walls by the formation of which the cells 

 were individualised. This is the mode in which the end of 

 the fruit-branch", which is originally cushion-shaped, becomes 

 transformed into a pitcher-shaped organ (PI. X, fig. 6).* 

 The cells of the inner surface of its cavity are from four to 

 eight times narrower than those adjoining them. This 

 arises from a division of the cells of the inner surface, by 

 means of longitudinal and transverse septa perpendicular to 

 the free surface, which takes place after the last division of 

 the cells adjoining them. These narrower cells expand into 

 long papillae directed rectangularly inwards, which almost 

 entirely fill the cavity of the fruit-sac (PL X, figs. 6, 8).t 



Shortly before the commencement of the dissolution of 

 the transverse septa of the string of cells which occupies 

 the longitudinal axis of the neck of the archegonium of 

 Fossombronia pusilla, a small free cell becomes visible in 

 the middle cell of the ventral portion of the archegonium, 

 occupying about an eighth part of the cavity of the latter 

 cell, and near its very distinct primary central nucleus. 

 The contents of this small free cell are transparent, and it 

 has a finely granular nucleus with no nucleolus. There 

 can be no doubt that this cell originates in free-cell forma- 

 tion round a secondary nucleus. In archegonia a little 

 more developed, this cell, which has considerably increased 

 in size, quite fills the lower third-part of its mother- cell. The 



* It is essentially the same process which makes the cavity of the ovary of 

 epigynous Phaneiogamia inferior, and by which the nucleus of many anatropal 

 ovules which have massive outer integuments, becomes sunk within the integu- 

 ments, except that in these cases, and especially in the latter, cell-formation 

 and cell-expansion are not so clearly distinguishable from one another as iu 

 Calypogeia. 



f Gottsche has given an elegant figure of a longitudinal section of a later 

 condition of the fruit-sac, 1. c, T. xxxi, f. 15. 



