422 HOFMEISTER, ON 



during its downward progress, a daughter-cell is formed in 

 its lower end, by the repeated bipartition of which, the 

 compound pro-embryo originates. It always happens in 

 Pinus Larioc, and frequently in P. syhestris, that one or 

 more of the germinal vesicles which are in contact with the 

 pollen-tube, but which remain unimpregnated, acquire firm 

 membranes of cellulose, and attach themselves to the tube, 

 but this phenomenon is not essentially connected with im- 

 pregnation.* 



The swelling which the pollen -tube of Taccus baccata 

 forms above the top of the endosperm often attains di- 

 mensions equalling that of the latter. Where much pollen 

 has fallen, several pollen-tubes almost always penetrate into 

 the ovules. These tubes swell and press against one another, 

 so that they not only fill the entire cavity above the en- 

 dosperm, but pass beyond it, sending forth prolongations 

 of different forms. Cases occur in which the swollen ends 

 of numerous pollen-tubes grow round the endosperm on 

 all sides, and meet underneath it, thus smothering it by 

 cutting off the access of nutriment. Even before the cor- 

 puscules are fully developed one, or more rarely two, large 

 spherical cells are formed in each pollen-tube. These cells 

 have no firm membranes, and are filled with a thickly- 

 fluid finely- granular protoplasm which encloses a central 

 nucleus. These cells at first float quite freely in the in- 

 terior of the pollen-tube. They are often surrounded by a 



* Scliaclit (' Beitrage zur Anatomie,' &c, Berlin, 1854, p. 287, 'Das Mikro- 

 skop,' 2nd edit., Berlin, 1855, p. 151, 'Elora,' 1855) arrived at a conclusion to 

 some extent in accordance with the above, inasmuch as it assumed the descent 

 of the rudiment of the pro-embryo from the upper end of the corpusculum to 

 the lower. In the 'Elora' for 1855 I have attempted to show that Schacht's 

 conclusions are incorrect. The objects which he took for the rudiments of the 

 pro-embryo cannot in the nature of things be what he supposed. 



Geleznoff 's statements as to the formation of the embryo of Larix are more 

 opposed to mine. He considers that the cell attached to the pollen-tube grows 

 by degrees out of the apex of the latter, and he assumes that the two communi- 

 cate by an open pore, and that the first cell of the pro-embryo originates in the 

 lower end of this cell. In all these points my observations gave a negative 

 result. I believe that I may place great reliance upon them, not only on account 

 of my investigations having been carried on for three years, but because my 

 numerous observations were repeated and verified during a sojourn in the Alps, 

 where, from the opportunities which existed for collecting cones at places of 

 different altitudes, the various stages could be followed out much more easily 

 and with greater certainty than could be done in a flat country. 



