THE INITIATION OF STAMINAL ZYGOMORPHY. 703 



EXPLANATION OF FIGURES IN PLATES. 



Fig. 1. A flower of Greyia Sutherlandii (Hook, and Harv.) viewed from the left posterior side, and 

 showing maximum elongation of filament, and anther-dehiscence of extreme right stamen of the anterior 

 group. X IJ. 



Fig. 2. An outline sketch of the same. A dotted line passes through the anthers of the anterior 

 stamen-group, x 1|. 



Fig. 3. Posterior stamen-group of antero-posteriorly zygomorphic bud of Greyia Sutherlandii represented 

 in fig. 4. Viewed from the posterior side. x about i. 



Fig. 4. A young flower of Greyia Sutherlandii from which the perianth has been removed. Viewed 

 from the posterior side. The antero-posterior zygomorphic condition of the androecium is shown, x about 2. 



Fig. 5. Anterior stamen-group of antero-posteriorly zygomorphic bud of Greyia Sutherlandii represented 

 in fig. 4. Viewed from the posterior side. x about 4. 



Fig. 6. A flower of Greyia Sutherlandii viewed from the posterior side. Three of the anterior stamen- 

 group are fully elongated, and their anthers have dehisced. x 1^. 



Fig. 7. An outline sketch of the flower of Greyia Sutherlandii represented in fig. 6. A dotted line 

 passes through the posterior stamen-group. x 1^. 



Fig. 8. A young flower of Greyia Sutherlandii from which the perianth has been removed. Viewed 

 from the posterior side. Lateral zygomorphy has been initiated. x about 1|. 



Fig. 9. Posterior stamen-group of laterally zygomorphic bud of Greyia Sutherlandii represented in fig. 8. 

 Viewed from the posterior side. x about 2^. 



Fig. 10. Anterior stamen-group of laterally zygomorphic bud of Greyia Sutherlandii represented in fig. 8. 

 Viewed from the posterior side, x about 2|. 



Fig. 11. A flower of Greyia Sutherlandii viewed from the posterior side. Eight stamens are fully 

 elongated, and their anthers are dehisced. The stigmatic surface is exposed. The shortest stamen is the 

 posterior one. x 1|. 



Fig. 12. An outline sketch of the same. A dotted line passes through the anthers of the posterior 

 stamen-group. x 1|. 



Fig. 13. A bud of Rhododendron argenteum L. from which the perianth has been removed. The 

 flower is viewed from the posterior side, and the androecium is laterally zygomorphic. x 8. 



Fig. 14. An expanding flower of Staphijlea pinnata L. Viewed from the posterior side, x IJ. 



Fig. 15. An expanding flower of Greyia Sutherlandii from which the perianth has been removed. It 

 is viewed from the posterior side. The androecium is markedly laterally zygomorphic. x about 1^. 



Fig. 16. A flower of Verhasciim tkapsus L. viewed from the left side. The greater part of the corolla 

 has been cut away. The long stamens are the anterior lateral ones, the short one is the posterior stamen. x 8. 



Fig. 17. A flower of Aquilegia vulgaris L showing filament-elongation and anther-dehiscence of second 

 group of stamens. 



Fig. 18. A flower of Aquilegia vulgaris L. showing filament-elongation and anther-dehiscence of first 

 group of stamens. 



Fig. 19. A flower of Aquilegia vulgaris L. showing stamens in various stages of filament-elongation. 



Fig. 20. A median longitudinal section — not quite radial~-of a stamen of Staphylea pinnata L. 

 Each longitudinal row of filament ground-cells consists of about fifty-eight cells. The loculus contains 

 pollen-grains, x 24. 



Fig. 21. A diagram to illustrate the relative lengths of the stamen-filaments in fig. 1. A circle has been 

 placed round the number indicating the stamen whose anther has dehisced, 



Fig. 22. The corresponding diagram for fig. 6. 



Fig. 23. The corresponding diagram for fig. 11. 



Fig. 24. A floral diagram of Greyia Sidlierlandii. The flower was borne loio on the raceme. The 

 lateral zygomorphy of the androecium is fairly pronounced. 



Fig. 25. A floral diagram of Greyia Sutherlandii. The flower was borne high on the raceme. The 

 lateral zygomorphy of the androecium is very pronounced. 



TRANS. ROY. SOC. EDIN., VOL. XLIX., PART III. (NO. 12). 95 



