ORGANS OF REPRODUCTION. 



255 



The pores, like the slits, also vary as to their number. Thus 

 we commonly find one in Monocotyledons, as in the Grasses, 

 and three in Dicotyledons. Sometimes a^^ain the pores are very 

 numerous, in which case they are either irregularly distributed, 



Fig. 656. 



Fig. .=554. Elliptical pollen of 

 y\\]V.y/0TtlPi)lygala). e. Ex- 

 tine. /. Slits. Fig. 555. 



The same polleu viewed 



fnim above. Fig. 556. 



Pollen-cell of Dacty'lis glo- 

 vierata. After Jussieu. 



or arranged in a more or less regular manner. The pores, again, 

 may be simple, or provided with little lid-like processes, as in the 

 Passion-flower (fff. 657, o, o, o), and Gourd {fig. 658). These 

 processes {fig. bb%, o, o) are pushed off by corresponding pro- 



Fia. 557 



Fig. 559. 



Fig 557. Pollen of Che Pa;islnn flower iPa^^'/orai, before bursting, o, o, o. 



Lid-like processes. F/fir. 558. Pollen of the Gourd, at the period of 



hiir«tin?. o, o. Lid-like processes of the e.xtine protruded by ihe pro- 

 jections, t, t, of the intine. From Jussieu. Fig. 559. Trigonal pollen 



of the Evening Primrose (CEnothera biennis). 



I'ections of the intine, t, t, when the pollen bursts, or when it 

 falls upon the stigma for the purpose of impregnating the ovules ; 

 hence such pollen-cells have been termed ojperculate. The pollen 

 of all Angiospermous plants (see 0^-^^le) is a simple cell as above 

 described, but in Gymnospermous plants the pollen is not a 

 simple cell, but it contains other small cells, which adhere to 

 the inside of its internal membrane close to the point where 

 the external membrane presents a slit. 



2. Contents of the Pollen-cells, or Fo villa. —The matter contained 

 within the coat or coats of the pollen-cell is called the fovilla. 

 It is a semifluid granular protoplasm in which are suspended very 

 small starch granules, and what appear to be oil globules. As 

 the pollen-cell approaches to maturity, the fovilla becomes more 

 concentrated, and contains less fluid matter and more granules. 



