58 Mr. A. Henfrey on the Progress of Physiological Botany: 



low, so that this cell (the germinal vesicle) is' thus changed into 

 an ovate body composed of three or four cells lying one above 

 another. Of these secondary cells the two situated at the two 

 rounded extremities are of greater diameter than those lying in 

 the middle. Each of them contains a nucleus. 



Contemporaneously with the growth and division of the ger- 

 minal vesicle^ the protoplasm collected at the base of the embryo- 

 sac forms itself into an irregular mass of roundish parenchymatous 

 cells, of which some frequently project into the central unoccupied 

 space of the embryo-sac, and even come in contact with the lower 

 end of the germinal body. In the course of the next two or 

 three days the germinal body increases in size so much that it 

 gradually comes to occupy the whole embryo-sac, displacing the 

 cells contained in its lower end ; its diameter is now about ^^^th 

 of a millimetre. At the same time a longitudinal septum is 

 formed in the lowest cell of the germinal body, and soon after 

 in the next above it. 



The lower end of the pollen-tube, the swollen, blind extremity 

 of which is about y^^ of a milhmetre in diameter, undergoes no 

 change during this time. 



The lower cells produced by the division of the germinal ve- 

 sicle grow faster than the upper, so that the form of the struc- 

 ture is changed from ovate to clavate, the larger end downward. 



The cells of the upper end now grow upward and form trans- 

 verse septa, finally passing out through the canals and the mouth 

 of the ovule, as described by Amici, in the shape of a confervoid 

 filament or articulated hair. Originally the end of the pollen- 

 tube lies beside this, so that they cannot be mistaken one for the 

 other. Simultaneously the cells of the lower end multiply and 

 form an enlarged body, the cells of which are filled with a dense 

 mass of granules ; this opake cellular nucleus is of course the 

 embryo. The hair-like prolongation of the upper end is distin- 

 guished both by its cylindrical form and the transparency of its 

 cells, which merely contain watery fluid with a small quantity of 

 finely granular protoplasm and a cell-nucleus. When the ger- 

 minal vesicle has thus become developed into the embryo and its 

 filamentous appendages, the pollen-tube disappears, apparently 

 by absorption. At the time when the filamentous appendage 

 becomes elongated, a deposit of spiral fibres occurs in the cells of 

 the outer coat of the ovule, and the seed proceeds rapidly toward 

 maturation. 



Comparing these observations with Amici' s, it will be seen that 

 they only differ in one point of very small importance, which re- 

 fers to the mode in which the embryo- sac displaces the nucleus. 

 Prof. Von Mohl deduces from them the conclusion, " that we must 



