

THE FLOWER 81 
The pollen-sacs, or microsporangia, contain the pollen grains 
or microspores. Hach pollen 3 
grain has— 
(a) An outer coat, the ex- 
tine, which gives rise to two. 
large lateral outgrowths, called 
“wings”; these are air-cham- 
bers, which make the pollen 
grains light, enabling them to Fic. 49,—PoLLEN GRAINS, 
be carried by the wind. PINUS. 
(b) An inner coat, the intine. % extine ; 7, intine ; c, central 
(c) The central body, con- eee 
sisting of protoplasm and nucleus; a pollen grain is thus 
| a cell with the 
essential struc- 
ture of a unl- 
cellular plant. 
By the time 
the pollen 
grains are 
fully formed 
the scales of 
the cone are 
widely — separ- 
ated from one 
(- another, 80 
| that the pollen 
grains fall in 
between — the 
scales. 
Fig. 50 repre- 

OV 

Fic. 50,—CArpetLaArRy Cone or Pinus, Mepran sents, to a cer- 
Section. (Low power. ) tain extent dia- 
grammatically, 
a median longi- 
tudinal section of a young cone. It consists of (1.) a stem ; 
(ii.) scales borne by the stem. These scales are of two 
s, stem; 0b, scaly bracts; 0, ovuliferous scales ; 
ov, ovule. 
