253 THE PHENOMENON OF 



contents are metamorphosed into a fructification-cell ; 

 therefore that they have a vegetative existence, short 

 though it be, previously to the fructification. In the later 

 behaviour, the difference presents itself, that the gonidium 

 leaves its mother-cell by slipping out, while the spore 

 appears to tear away the membrane of the mother-cell 

 with it. The formation of the fruit-club of Saprolegnia 

 also belongs here. The process of shutting off the apex 

 may be repeated many times, in a retrogressive order, 

 in the same cell, as occurs not unfrequently in Saprolegnia, 

 where a second, and often a third piece of the cell is 

 developed, underneath the first fruit-club, into a gonidium- 

 case or spore-case (both are met with). Or the shut- 

 ting off is repeated in an apex reproduced by a growing 

 through of the emptied fruit-sac, as likewise occurs in 

 Saprolegnia (particularly S. ferax, S. proli/era) and in 

 Vaucheria clavata* 



(3. With a nucleus. A remarkable example of this 

 is furnished by the origin of the sacculate appendage of 

 the embryo-sac of Bartonia, described by Hofmeister.f 



The upper end of the embryo-sac (the mother-cell of 

 the germinal vesicles and endosperm-cells), after three 

 free germinal vesicles have been formed in it, produces a 

 prolongation penetrating into the canal of the micropyle, 

 which, after the previous formation of a nucleus, becomes 

 shut off from the embryo-sac as a separate cell. In general 

 the primary nucleus of the embryo-sac is not dissolved 

 during this process. The first division of the germ-cell (the 

 germinal vesicle) of the same plant | affords another 

 example. The originally roundish, nucleated germinal 

 vesicle becomes elongated in the form of a tubular cell, 

 the nucleus at the same time vanishing. In the front 

 part of the cell, turned away from the micropyle, a some- 

 what flattened nucleus is now formed, and in consequence 

 of this a separation of this anterior extremity as a dis- 



* Vide Unger, 1. c, fi^. 13. 



f ' Enstehung des Embr. der Phanerog.,' p. 39, t, ii, f. 34 — 40. 



X liofmeister, 1. c, p. 40, t. iii, f. 4 — 11. 



