288 



THE NURSERY-BOOK. 



perfect or contain only one sex. When the sexes are borne in 

 different flowers upon the same plant, the species is said to 

 be monoecious ; and 

 when they are borne 

 upon different plants 

 the species i s dioe- 

 cious. Sometimes 

 the inflorescence is 

 mixed, some flowers 

 being perfect, some 

 staminate and some 

 pistillate, all upon 

 the same plant ; such 

 species are polyga- 

 mous. Most garden 

 plants have perfect 

 flowers. Many nut- 

 bearing trees are 

 monoecious, as wal- 

 nuts, butternut, 

 hickories, chestnuts, 

 hazels and filbert 

 and oaks. Some of 



the composite plants are also monoecious, the large head bearing 

 staminate flowers in one part and pistillate in another. Pump- 

 kins and squashes are monoecious and so are most varieties of 

 melons. Fig. 91 shows a pistillate pumpkin flower with the 

 ovary or young pumpkin below, and Fig. 92 a staminate flower 

 which lacks the enlargement below. Among dioecious species 

 may be mentioned the willows and poplars. 



The ovary contains the ovules. When these are acted upon or 

 fertilized by the pollen they develop into seeds. The pollen falls 

 upon the stigma or upper extremity of the pistil, and each 

 grain germinates and sends a tube down through the style to an 

 ovule. The stigma is a slightly roughened soft surface, and 

 when it is "ripe," or ready to receive the pollen, it becomes 

 slightly moist or sticky. In most plants the stigma is merely 



Fig. 91. Pistillate Squash flower. 



