PINE REPRODUCTIVE ORGANS 147 



c. Cones larger than (), bVown and with lignified tissues : 

 on these the scales are usually more or less separated from one 

 another, so as to disclose the seeds, two of which are borne 

 at the base of each of the ovuliferous scales. These ripe 

 cones are seated laterally near the apex of the two-years-old 

 shoot. 



I. Cut median longitudinal sections of a cone corresponding 

 to stage (a). It should previously have been hardened with 

 alcohol for some days : mount in glycerine, and examine with 

 a low power. Observe 



1. The central axis, not differing essentially from the young 

 vegetative axis : on this are borne scales of two orders easily 

 distinguished by their size. 



2. The smaller of these are the leaves borne by the axis of 

 the cone, and the morphological equivalents of the brown scale- 

 leaves which cover the winter buds. 



3. In the axil of each of these is borne one of the larger or 

 ovuliferous scales, which are longer and more bulky than 

 (b) : they alone can be seen externally. On the upper surface 

 of each of these, close to the axis, are borne 



4. Two ovules or macrosporangia, which are anatropus, so 

 that the micropyle is directed towards the base of the scale : if 

 cut in a median plane, each ovule will be seen to consist of 



i. One integument, several layers of cells in thickness, with 

 a widely open micropyle facing the axis : this surrounds 



ii. The nucellus, a mass of parenchyma, near the centre of 

 which is 



iii. The embryo-sac or macrospore, a cell much larger than 

 those of the surrounding tissue, and lying some distance below 

 the apex of the nucellus. 



Pollen-grains may often be found seated on the apex of the 

 nucellus : one or more of these may throw out pollen-tubes, 

 which penetrate into its tissue. 



Dissect off one whole ovuliferous scale, and observe on its 

 upper surface, close to the base, two ovules, which are 

 anatropous. Note also the relative positions of the two sets of 

 scales. 



II. Take cones of the stage above described as (b). The 



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