black: inflorescence and fruit of pyrus malus 529 



with well-developed sepals. The primordia of the petals and 

 stamens are also shown. The intercalary growth of the torus as 

 well as the terminal growth of the members produced upon it 

 emphasizes the cup-shaped appearance, so that the floral members 

 are elevated considerably above the apex of the axis, which persists 

 in the center of the flower. In figure 4 the petals, stamens, and 

 pistils are formed. Figure 5 shows two buds from an inflorescence 

 with the primordia of all parts established. The petals develop 

 in a circle within the sepals and alternate with them. In a young 

 flower the tips of the scale-like petals curve over the torus, as 

 shown in plate 35, figures 6 and 7, and plate 36, figure i. 

 In the mature flower the tips overlap as found in plate 36, figure 

 2, forming an arch over the stamens and pistils. The sepals are 

 lined with hairs, whereas the petals are practically free from hairs. 



The stamens next develop in three circles. The stamen first 

 appears as a blunt outgrowth of the torus. As the successive 

 circles develop, the stamen is differentiated into anther and 

 filament. The filament varies in length, according to the position 

 of the stamen. Sections of stamens in position are shown in 

 PLATE 35, figures 3 to 7, and in plate 36, figures i and 2. It 

 will be seen that the anther is conspicuous from the first. The 

 anther develops as a four-lobed structure as shown in plate 36, 

 figures 3 and 4, which are cross sections of anthers in slightly 

 different stages of development. The vascular strand in the 

 connective appears denser than the surrounding tissue and in 

 each lobe of the anther a few cells are found which are larger than 

 the others and have dense contents. This is the primary sporo- 

 genous tissue in which the tapetum is early recognized. The cells 

 within the tapetum become the microspores or pollen grains. The 

 anther in figure 4, plate 36, is a little older than that in figure 

 3 and a little more specialization is shown in the anther wall in the 

 region where the longitudinal dehiscence will occur. The cells in 

 this portion of the epidermal layer are smaller with dense cell con- 

 tents and inconspicuous cell walls. 



As the anther may not be formed by the end of the first year, 

 the pollen does not necessarily pass the winter in the pollen- 

 mother-cell stage as reported by Drinkard (7) for Virginia or by 

 Kraus (6) for Oregon. If the anther is not formed the first year 

 there is no resting period following the pollen mother cell stage, 

 35 



