CONIFERM. 



513 



Angi(?sperms; in Araucana and Dammar a, on the other hand, the long sausage- 

 shaped pollen-sacs hang in larger numbers free beneath the peltate limb. The 

 wall of the pollen- sacs is usually delicate, and finally dehisces longitudinally to 

 allow the escape of the pollen-grains, which are produced in extraordinarily large 

 numbers, since they have usually to be carried by the wind to the female organs 

 of the same or of another tree. The pollen-grains which happen to fall on the 

 opening of the micropyle of the ovules are retained by an exuding drop of fluid, 

 which about this time fills the canal of the micropyle, but afterwards dries up. 



Fir,. 348. — 7 axus baccata ; A male flower (mag^nified), 

 a the pollen-sacs ; B a stamen seen from below with open 

 pollen-sacs ; C piece of a foliage-shoot with leaf (^, from the 

 axil of which springs the female flower, s its envelope of 

 scales, sk the terminal ovule ; D longitudinal section of the 

 same (magnified), i integument, kk nucellus of the ovule, 

 X a rudimentary axillary ovule ; E longitudinal section 

 through a more mature ovule before fertilisation, j integu- 

 ment, kk nucellus, e endosperm, m aril, s upper scales of 

 the envelope. 



Fig. ■^Ag.—yuntperns communis; A longitudinal 

 section of a male flower, B (upper figure) a stamen seen 

 from the front and the outside, (lower figure) seen from 

 the back of the axis; Clongitudinal section of a female 

 flower; a the pollen-sacs, j the peltate lamina of the 

 stamen, b lower leaves of the floral axis, c carpels, 

 sk ovules, kk nucellus, i the integument (A and C X 

 about 12). 



and thus draws the captured pollen-grains to the nucellus, where they immediately 

 emit their pollen-tubes into its spongy tissue. In the Cupressineae, Taxineae, and 

 Podocarpese this contrivance is sufficient, since the micropyles project outwardly; 

 in the Abietineae, where they are more concealed among the scales and bracts, 

 these themselves form, at the time of pollination, canals and channels for this 

 purpose, through which the pollen-grains arrive at the micropyles filled with fluid 

 ((/". Strasburger, /. <:.). The large number and lightness of the pollen-grains enables 

 them to be carried great distances by the wind; in the true Pines and the Podo- 



l1 



