262 WALL OR COATS OF THE POLLEN. 
in some cases we find twelve or more slits. These slits are gene- 
rally straight (jig. 568, f), but in Mimulus moschatus they are 
curved ; and other still more complex arrangements occasionally 
occur. 
The pores, like the slits, also vary as to their number. Thus 
we commonly find one in Monocotyledons, as in the Grasses ; 
ie 7/16 Fig. 572. Fig. 573. 
Fig. 571. Pollen of the Passion-flower (Passifiora), before bursting. 9, 9, 0. 
Lid-like processes. Fig. 572. Pollen of the Gourd, at the period of 
bursting. 0,0, Lid-like processes of the extine protruded by the projec- 
tions, ¢, ¢, of the intine. From Jussieu.— /ig. 573. Trigonal pollen of the 
Evening Primrose (@nothera biennis). 
and three in Dicotyledons. Sometimes again the pores are 
very numerous, in which case they are either irregularly dis- 
} tributed, or arranged in a more or less 
Fic. 044, regular manner. The pores, also, may 
be either simple, or provided with little 
lid-like processes, as in the Passion- 
flower (fig. 571, 0, 0, 0), and Gourd (fig. 
572). These processes (fig. 572, 0, 0) 
are pushed off by corresponding pro- 
jections of the intine, t, t, when the 
pollen bursts, or when it falls upon the 
stigma for the purpose of fertilising the 
ovules; hence such pollen-cells have 
been termed operculate. 
The pollen of all Angiosperms is 
usually regarded as a simple cell as 
above described, but in Gymnosperms 
Fig. 574. Pollen of Spruce Fir the pollen is not a simple cell, but it 
phim s Ga is contains other small cells, which adhere 
lateral cells, #1, which are to the inside of its internal membrane 
simply vesicular protru- close to the point where the external 
sions of the extine, e. 1. ' i 
Intige. y. The apical celi Membrane presentsa slit. These minute 
which forms the pollen- cells are termed daughter-cells. The 
fasarc according to ste recent investigations of Elfving have 
burger), of the male pro- also shown that in some cases, at least, 
thallium incontact withthe the pollen-cell of Angiosperms is not 
intine. After Schacht. , 
unicellular as generally regarded, but 
that before it escapes from the anther there is formed in ita 
mass of very smatl cells, which appear to be functionless, while 
