FORMATION OF THE POLLEN. 259 
brane which is in direct connexion with the cellulose coat of the 
mother-cell ; and thus constitute what are known as the ‘ special 
mother-cells.’ Finally, each protoplasmic mass of the special 
mother-cells separates from the cell-wall and secretes around 
itself a membrane, so that ultimately we have four perfect cells, 
d, which constitute the true pollen-cells, formed in each parent 
cell. 
As these pollen-cells progress in development, and increase 
in size, they distend the wall of the mother-cell, and ultimately 
cause its absorption; and subsequently, by their continued 
growth, the walls of the special mother-cells are generally ab- 
sorbed also, by which the pollen-cells are set free in the cells of 
the anther. Sometimes the membrane of the special mother- 
Fia. 560. Fic. 561. Fic. 562. 
Fic. 563. 
Fig. 560. Formation of the pollen in the Hollyhock (Althcea rosea). After 
Mohl and Henfrey. a shows four nuclei in the parent cell, and four septa 
commencing to be formed. The primordial utricle and cell-contents are 
contracted by the action of alcohol. 6. The development of the septa more 
advanced. c. The primordial utricle removed from the parent or mother 
cell, but not yet completely divided into four parts. d. The division of 
the parent or mother cell into four parts completed, and each part con- 
taining one pollen-cell.—— Fig. 561. Pollen of Jaga anomala.— Fig. 562. 
Pollen of Periploca greca. After Jussieu.— Fig. 563. Mass of spherical 
pollen-cells from a species of Acacia. 
cells is not completely absorbed, in which case the pollen-cells 
of the mother-cel! are more or less connected, and form a com- 
pound body consisting of four pollen-cells, as in Periploca greca 
(fig. 562); or if the membranes of two or more united mother- 
cells are also incompletely absorbed, we may have a mass con- 
sisting of eight pollen-cells, as in Inga anomala (fig. 561); or 
of some multiple of four, as in many species of Acacia (fig. 563). 
In the Onagracez, the pollen-cells are loosely connected by long 
viscid filaments or threads, which seem in this case to be wholly 
derived from a secretion left by the imperfect solution of the 
mother-cells; while in the Orchidacez the pollen-cells cohere 
in a remarkable degree and form pollen-masses which are com- 
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