INTRODUCTION 35 



perianth), but also the need for subsequent fertilisa- 

 tion has evoked the variation in the pollen-grains 

 and the ovules. The structural differences in the 

 seed or fruit are correlated with the survival of the 

 seed during the dormant period and its effective 

 germination afterwards, hence the presence or absence 

 of endosperm. By some the difference in the 

 number of cotyledons is connected with a difference 

 in habitat. Monocotyledons being considered as 

 adapted to aquatic conditions. 



15. The Natural History of the Plant. 



Properly the term Natural History is best used to 

 denote the study of Biology or life, and Geology, 

 or that of the earth,, including in the last minera- 

 logy, petrology, or the study of minerals and 

 rocks. 



But the term has been applied in a more restricted 

 sense to the study of the life-history of living things. 

 A better word is bionomics, as it implies that the 

 study is that of the activities and behaviour of a 

 living organism. 



This study applies alike to plants and animals. 

 In the case of plants it is necessary to start from the 

 commencement of the visible stages in the plant's 

 development. This is seen in the germination of 

 the seed. The various stages which it goes through 

 in bursting from the seed-coat, and the penetration 

 of the soil by the radicle, with the later emergence 



