282 BOTANY FOR BEGINNERS CHAP, xx 



A natural order consists of a number of genera which possess some 

 common character. 



A genus consists of one or more species which resemble one another 

 in one or more respects. 



A species includes plants which must have descended from a common 

 ancestor. 



QUESTIONS ON CHAPTER XIX AND XX. 



(1) What are the chief distinctions between Monocotyledons and 

 Dicotyledons? (1898.) 



(2) Describe and compare the corollas of any three of the following 

 plants, and mention the natural order to which each plant belongs 

 Larkspur (Delphinium), Monkshood (Aconitum), Sweet Pea (Lalhy- 

 rus), Deadnettle (Lamium), Snapdragon (Antirrhinum). (1892.) 



(3) Describe and compare the fruits of the Wallflower (Cheiranthus) 

 and the Pea (Pisum), and those of the Parsley (Petroselimini] and the 

 Dandelion (Taraxacum). To what natural orders do these plants re- 

 spectively belong ? ( 1 892. ) 



(4) Describe the general structure, position, and placentation of the 

 ovary in the Umbelliferoe, the Leguminosse, and the Labiate. (1891.) 



(5) Describe the position, number, and arrangement of the stamens 

 in the flowers of the Cruciferce, the Composite, and the Primulacese. 



(1891.) 



(6) Give a general account of the structure of the flower of a Legu- 

 minous plant. (1899.) 



(7) Describe carefully the structure of a leaf bud in any member of 

 the natural order Cupuliferoe. (1899.) 



(8) Describe the arrangements of the stamens in the flowers of the 

 Buttercup, the Deadnettle, and the Sweet Pea. Refer these plants to 

 their natural orders. (1894.) 



(9) Mention instances from the following natural orders of flowers, in 

 which the number of the stamens is (a) less than, or (b) greater than, 

 that of the petals, explaining in each case how the difference in 

 number arises Ranunculaceas, Cruciferoe, Scrophularineae, Labiate. 

 (1890.) 



(10) Describe with examples (a) a hypogynous, (b) a perigynous, 

 and (c) an epigynous flower. (1886.) 



( 1 1 ) What is a placenta ? Describe the placentation in the Cruciferoe, 

 the Leguminosie, and the Liliaceoe. (1887.) 



(12) How do the plants of the natural order Amaryllideoe differ from 

 those of the Liliaceae ? 



