EXPERIMENT WITH A PLANT 147 



appears to the naked eye as a fine yellow dust, 

 but the individual grains composing it can easily 

 be seen by the aid of a small hand lens. 



If the ovary be slit by a vertical incision, it 

 will appear to be — what, indeed, it actually is — the 

 future pod in miniature. It is almost exactly like 

 the ripe pod full of peas ; everything is there, but 

 in miniature ; the whole pod is not longer than 

 one-third of an inch. Inside each of the miniature 

 peas is a minute cell, the female reproductive cell, 

 or egg, or ovule. 



Before such an egg can develop it must unite 

 with or, in other words, be fertilised by a male 

 reproductive cell. In the case of a great many 

 plants there are special arrangements by which the 

 eggs are always fertilised by pollen from another 

 flower, the pollen being transferred by the agency of 

 the wind, or by that of insects. This is what is 

 known as cross-fertilisation. But in the pea, and 

 in many other plants as well, the ovules in a parti- 

 cular flower are fertilised by the pollen from the same 

 flower. This is known as self-fertilisation. But the 

 essential process in the two cases is the same : it is 

 the union of a male with a female reproductive cell. 

 In all cases of biparental reproduction, which is all 

 we are concerned with in this book, both in plants 

 and in animals, fertilisation consists essentially in 

 this union of a male with a female reproductive cell, 

 and until this union has taken place the develop- 

 ment of the egg into the future plant or animal 

 cannot proceed. 



