POLLEN AND POLLINATION. 371 



guished as fruit-scales. At the base of the fruit-scale, right and 

 left, is found on each side of the rib an ovule (s), with its micro- 

 pyle turned below and towards the outer side. The edge of the 

 simple ovular integument is prolonged at the micropyle into two 

 lobes (ra), placed right and left. Bract and fruit-scale have grown 

 together at the base, and are therefore removed together from the 

 axis of the cone. The cones of the Abietineae, and other true 

 cone -bearing Coniferae, are conceived to be either single flowers or 

 inflorescences, according to the significance which is attached 

 to the fruit-scale. This may either be considered as a flattened 

 metamorphosed axial shoot, growing in the axis of a modified leaf, 

 which we have here called the bract, and partially adnate to the 

 bract ; or, as a development of the placenta of a carpellary 

 leaf, which we have hitherto called the bract. In the former case, 

 therefore, we should have a bi-ovular branch in the axil of 

 each bract ; in the second a bi-ovular placenta on the upper side of 

 a carpellary leaf. In the former case, the cone would therefore 

 be an inflorescence composed of many fertile axillary branches ; 

 in the second, the cone would be a single flower composed of 

 numerous open carpellary leaves. 



Pollination. The remarkable structure of the fruit-scale is 

 explained by the machinery for pollination, which can be followed 

 upon fresh material only, and at the time of pollination. As soon 

 as the male flowers begin to free their pollen (which is carried off 

 by the wind), we can demonstrate an elongation of the axis of 

 the cone, whereby the fruit-scales, together with the bracts apper- 

 taining to them, are separated from one another. The pollen can 

 now fall upon the uplifted fruit-scales, slip down them, and 

 guided by the projecting rib, come between the two prolongations 

 of the ovular integument. Later on, these prolongations curve 

 inwards, and in this way carry the pollen into the micropyle, 

 and to the apex of the nucellus. After full pollination the fruit- 

 scales soon close their edges together, and these are consolidated 

 by the intergrowth of papillae. The bracts do not further develop, 

 nor does the central rib of the fruit-scale, which is of no further 

 use. The red colour of the cone changes into brown, and then 

 into green (when ripe, again becoming brown) ; and the cone 

 slowly bends over, and finally takes a pendant position. 



The Ovule and Embryo-sac. We will now turn our attention 

 to the further changes which take place in the pollinised ovules of 

 the Coniferae. At the time of pollination the embryo-sac of the 



