PLATE X.— BIRCH (Betula), HAZEL (Corylus), OAK (Quercus), and WILLOW (Salix). 



These four well-known Trees, chosen to illustrate the simpler forms of flowers among Dicotyledons, have this in common, that the 

 flowers are small and simple, male and female being separate and arranged in different spikes which fall away after flowering: hence 

 commonly called Catkins. The Male Flower consists of Stamens, and the Female of Carpels, to which may be added a Perianth more 

 or less obvious. There are also frequently a number of investing Bracts connected with the flowers which have an interest in the 

 detailed comparative study of plants, but for our present purpose are mere accessories — not essentials. 



The Birch and Alder, Oak and Hazel, are wind-fertilised, and the pollen is therefore dry and powdery, falling from the male catkins 

 like showers of fine dust, and the male and female flowers are on the same tree. But in the Willow, which is insect-fertilised, the golden- 

 yellow pollen is not dry and powdery, and the two kinds of flowers are on separate trees.. 



Common Birch (Betula alba), flowers in spring. 



Fig. 1. Male and Female Catkins on the same tree, the female being smallest 

 Fig. 2. Detach a scale from male catkin and examine. 



There are two small scales overlapped by a larger one, and each of the three bears its own stamens. 

 Fig. 3. Detach a small scale with its accompanying stamens from inside of large scale. 



There are two Stamens with branching filaments. 

 Fig. 4. Stamen detached, showing Filament branching. 

 Fig. 5. Detach one of the scales from female catkin. 



Three scaly bracts are united at time of flowering, each with a female flower in its axiL 

 Diagram I. — There are three flowers in a group, with three overlapping scales, the largest in the middle. 



(a.) Male Flower — each consists of two Stamens, the filaments of which fork, and so give rise to the appearance 



of four Stamens. 

 (b.) Female Flower — each consists of two Carpels united. 

 Diagram II. — Alder {Alnus). 



(a.) Male Flower — each consists of four unbranched Stamens and a Perianth of four Segments. 

 (b.) In the Female group the middle flower is absent 



Fig. 6. Winged Fruit — in the ripe catkin the scaly bracts are united and bear three winged fruits. 

 Fig. 7. Make a vertical section of the fruit parallel to the wings. 



Only one of the two Ovules has ripened into Seed, the other becoming aborted. 



Common Hazel (Corylus Avellana), flowers in early spring. 



Fig. 8. Male and Female Inflorescence on same tree, the female being small and bud-like with the crimson stigmas projecting. 

 Fig. 9. Detach scale from Male Inflorescence — outer view (not inner as on Plate). 



Wedge-shaped and hairy, with two smaller scales appearing on each side. 



Fig. 10. Examine inner side of scale. 



Male flower consisting of four Stamens with forked filaments, so that there are apparently eight stamens. 

 Fig. 11. Stamen detached and magnified. 



Filament forked, and Anthers hairy at the tip. 

 Fig. 12. Female Inflorescence enlarged. 



Fig. 13. Remove some of the outer scales and observe that they are barren, while the inner are fertile. 

 Fig. 14. Single flower detached from scale. 



Female flower consisting of two united Carpels, as indicated by the two long, separate Styles. There are indi- 

 cations of minute teeth surrounding upper part of Ovary, and these may be regarded as a very rudimentary 

 Perianth. 



Diagram III. — (a.) Male Flower consisting of four branched Stamens. 



There are three scaly Bracts, but only a single flower appears to be developed. 

 (b.) Female Flower consisting of two united Carpels, with a rudimentary Perianth. 



There are three small Bracts surrounding the flower, united towards their base and deeply cut at their 

 margins, forming the " husk " of the fruit 



Fig. 15. Fruit — a Nut A Filbert, for instance, may easily be procured and examined. 



Split the nut-shell in two lengthways, as shown, without injuring the seed. 



Shell hard and woody with scar at bottom^ to which fruit-stalk was attached, and mark left at top by the styles. 



Seed usually single, attached to bottom of shell by a brown, fibrous cord stretching from top of seed This 

 cord originally formed the axis between the two chambers of the Ovary, but by the excessive development of one 

 seed at the expense of all the rest, this has been displaced to one side. 



Fig. 16 Soak seed for a little in boiling water with a little washing-soda added, then the two coats of the seed may be removed 

 — an outer brown and an inner white — and the two cotyledons parted from one another. 

 Two fleshy Cotyledons. 

 Short Radicle at top. 

 Plumule continuous with radicle, and forming a terminal bud. 



Oak (Quercus Robur), flowers in spring. 



Fig. 17. Male and Female Inflorescence on same tree — the male slender and pendulous with numerous flowers, the female 

 stouter and upright 



Fig. 18. Male flower with lobed Perianth and ten Stamens, the filaments of which are not forked. 



Figs. 19 and. 20. Female flower entire and in section. 



Investment or cupule of numerous bracteoles. 



Perianth, toothed. 



Ovary, Style, and three-lobed Stigma 



