CHAPTER XXVII 

 THE FAMILIES OF THE ANGIOSPERMAE 



INTRODUCTION 



The Angiospermae of today are represented by plants showing the greatest 

 possible diversity of form. They occur wherever life is possible between the 

 equator and the poles, on land, in water and even in the sea. Many occur as 

 epiphytes and some as parasites. They range in size from minute floating 

 forms such as Wolffia arrhiza, to giant trees such as the Eucalyptus of 

 Australia. Many are dispersed over entire continents while others are 

 restricted to local areas or to small islands, and explorers have shown that 

 even small difl^erences of habitat may be sufficient to cause one species to 

 be replaced by another. 



Since the delimitation of species is often a matter of opinion, the total 

 number of species of Angiosperms cannot be accurately estimated but a 

 conservative reckoning would place it between 100,000 and 150,000. 



Out of this vast assemblage we shall select a few families for detailed 

 study, choosing those which are most characteristic of the British Flora. 

 Since however to study the British Flora alone would give a very imperfect 

 impression of the Angiosperms as a whole, we shall briefly refer to a wider 

 range of families under their respective orders and mention some of their 

 more interesting features. 



It must be borne in mind that in the study of flowering plants the sub- 

 ject should be considered as a whole and that the systematic treatment of 

 the group cannot be entirely divorced from the wider aspects of ecology, 

 bionomics, geographical distribution and economic importance. In 

 addition, the activities of the horticulturist in breeding, crossing and 

 selection have materially altered the appearance of many plants. The wild 

 Asparagus found on the rocky coast of our western seaboard, for example, 

 bears little resemblance to the succulent shoots which are sold in the green- 

 grocer's shop. 



The Angiospermae are divided into two series: Dicotyledones and 

 Monocotvledones, each of which is further subdivided into Orders and 

 Families. The following classification indicates the system of treatment 

 which will be followed in this book. A comparison of this system with that 

 adopted by various authorities will show certain differences. It would 

 clearly have been simple to follow any one of the accepted treatments, but 

 unfortunately they all differ markedly from one another, and all are open to 

 criticism in some respects. 



In general it may be said that while the present sequence of treatment is 

 intended to indicate a phylogeny from the more primitive to the more 



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