Proceedings of the Ohio State Academy of Science 79 



two distinct individuals tlie plant is dioecious. The stamens pro- 

 duce microsporangia and the carpels megasporangia or ovules. 

 In the angiosperms the carpel usually has three parts called 

 stigma, style, and ovulary. the ovules being completely inclosed 

 in the ovulary. Commonly all the carpels of the gynoecium are 

 grown together and in such cases a compound ovulary is pro- 

 duced with one or more cavities. 



Following a peculiar process known as reduction, which 

 takes place in the cells inside of the microsporangium, a consid- 

 erable number of microspores are developed, four for each origi- 

 nal cell. In nearly the same way, four megaspores one of which 

 survives, are usually produced in each ovule. The flowers are 

 thus modified spore-bearing branches or shoots producing two 

 kinds of nonsexual spores. The flowers are nonsexual organs 

 and the tree itself is always a nonsexual plant called the sporo- 

 phyte. The microspores germinate and develop into the pollen 

 grains and the megaspores into the so-called embryo sacs, or min- 

 ute, parasitic, male and female gametophytes respectively. After 

 pollination has taken place, which is simply the transfer of the 

 pollen to the ovules or the stigmas, a tube grows from the pollen 

 grain into the embryo sac. The two sperm cells produced in the 

 pollen grain or in the pollen tube pass down the tube and one 

 • unites with the egg cell of the female gametophyte. This union 

 of sperm and egg is called fertilization. The resulting cell which 

 is the oospore germinates and gives rise to an embryo inside of 

 the ovule, the whole finally constituting the body called the seed. 

 This embryo in the seed is the sporophyte and after sprouting 

 develops into the tree. The seed is produced inside of or in con- 

 nection with the modified carpels and other contiguous parts, the 

 whole being called the fruit. The fruits of our trees are of many 

 types usually with some adaptation for seed distribution, so that 

 the seed with its little embryonic tree inside may be carried away 

 from the parent plants to some other and perhaps more favor- 

 able environment. Here, if conditions are proper, it sprouts and 

 begins its life as an independent individual. The whole pro- 

 ■cess of flower, seed, and fruit production is exceedingly complex 

 and requires close study and observation if one would know the 

 more obscure activities going on during the life cycle of a tree. 



