156 NATURE TEACHING 



the central portion, and at first suggest petals. Where, 

 then, are the stamens, and the pistil ? Cut the head 

 through : the middle is seen to be made up of a number of 

 separate tubular bodies, each of which possesses its own 

 petals, stamens and pistil. The head is not a single flower, 

 but a collection of flowers. This is true of all the plants in 

 the large order to which the sunflower belongs, including 

 the daisy, groundsel, pyrethrum, Michaelmas daisy, etc. 



Experiments in Cross-fertilisation. 



Examine the separate pistillate and staminate 

 flowers of the cucumber or vegetable marrow, and learn 

 how to distinguish them before the flower-buds are 

 open. Watch them, and notice that the fruits are only 

 formed from pistillate flowers. Staminate flowers die 

 after shedding their pollen. 



Tie up two pistillate flower-buds (which are almost 

 ready to open) in separate bags made of tough paper (for 

 instance, flat sugar-bags), with a string put through them 

 as shown in Figs. 19 and 20. When one of these flowers 

 is open, pluck a staminate flower and remove its petals ; 

 uncover the pistillate flower, and gently touch its stigma 

 with the pollen-bearing portion of the staminate flower, 

 so that some of the pollen sticks. Replace the bag. 

 Leave the second pistillate flower tied up the whole 

 time. The first should form a ripe fruit, the second not. 



Select two plants of the same kind, but possessing 

 well-marked differences ; for instance, different-coloured 

 polyanthus, or begonia. Carefully cut, or pull off, from one 

 flower some of the stamens which are just shedding 

 their pollen, and carry them to the flower of the other 



