1 44 Flowers and their Unbidden Guests. 



to new conditions may involve simultaneously species 

 from the most various families of plants, there is no 

 difficulty in understanding why, for instance, in one 

 floral district numerous species from the most different 

 orders are found armed with thorns, while in another 

 there is a prevalence of flowers with very copious nec- 

 tar, and why, in short, the character of the whole 

 vegetation is often determined by the predominance of 

 plants that resemble each pther in some similar speci- 

 ality of structure. This conformity however is, on the 

 other hand, greatly limited by the extreme multifarious- 

 ness presented both by the means of attraction and 

 by the means of protection, and by the fact that one 

 and the same result can be attained by formations 

 of the most diverse kinds. This circumstance indeed 

 that, though the dangers to be guarded against are 

 identical, yet the means of defence may be provided 

 equally well by the most different formations, explains 

 how it is that several species of one and the same 

 group are often to be found growing side by side with- 

 out coming into direct competition with each other, 

 inasmuch as each has its own special advantageous 

 variety of organisation. Examples of this might be 

 adduced in abundance, especially were we to consider 

 the distribution of many Labiatse, Caryophyllacese, Sali- 

 einese, and Cirsiiims ; but by such discussions I should 

 fear to exceed unwarrantably the limits of this trea- 

 tise. I confine myself therefore to one single example. 



