154 
ORGANOGRAPHY. 
BOOK I. 
of which separated from the mass, which proved that a force 
of some kind held them together. Shortly after four append- 
ages, like knife blades, developed at equal distances on the 
inner face of the pollen cell, and gradually directed their edge 
towards the centre, so that they began by cleaving the granu- 
lar mass in four different lines, and finished by dividing it 
into four little triangular masses ; and when the appendages 
met in the centre they grew together, and divided the cavity 
of the pollen cell into four distinct cavities, which soon 
after rounded off their angles, and in a short time the little 
granular masses became spherical, like melted lead run into 
the hollow of a bullet-mould. The partition of the mass thus 
brought about by the appendages seems to me to indicate that at 
this period the mass was not protected by a special integument, 
and that the mutual adhesion of the granules was very weak. 
" When things had arrived at this point, the portion of the 
tissue formed by the pollen cells separated itself from the 
surrounding parts, and each pollen cell became loose, gene- 
rally in the form of a square parallelopiped with rounded 
angles; each little mass of granules gained a smooth, colourless, 
transparent membrane, which was at first membranous but 
afterwards became thick and succulent, and soon began to 
take on the characters peculiar to the pollen of the gourd. 
The integument began to bristle with fine conical papillae ; 
several roundish lids were traced out here and there on its 
surface ; it hardened, became opaque, assumed a yellow colour, 
ceased to grow, and attained its perfect maturity." Mirbel 
adds to this highly interesting statement, that he finds in the 
generality of plants that the mode of forming the pollen is 
much the same as in the Gourd. 
The granules of pollen are commonly distinct from each 
other. They are, nevertheless, in certain cases, found in 
various states of cohesion. In some plants they cohere in 
threes or fours, as in many Orchideae ; or in clusters of many 
grains, as in Acacia (Plate IV. fig. 28.). In some, as the 
Fuchsia, CEnothera, &c., they hang together by a sort of 
cobweb substance, which is the remains of the cellular matter 
in which they were engendered. In other cases they coalesce 
in masses, having a waxy texture and colour, and occupying 
