20 THE AMERICAN BOTANIST 



enough to kill a million and a half of guinea-pigs. Another 

 curious property of this poison is that if a dose too weak to 

 kill is given first, the strength can be gradually increased until 

 the subject can take, without ill effects, enough to kill ten 

 thousand others not accustomed to it. In the blood of such 

 immunized animals an antitoxin is formed, similar to that 

 formed when the body is attacked by bacteria, and this anti- 

 toxin can be used to render other animals immune. It is cer- 

 tainly a strange thing that one of the flowering plants should 

 possess properties so similar to those extremely simple or- 

 ganisms, the bacteria. 



Species of Hawthorn. — In the 6th edition of Gray's 

 Manual exactly ten species of our native hawthorns (Cra- 

 taegas) are given for the North Eastern States, but Edward 

 L. Greene asserts that there are a thousand species in this 

 region and the last edition of the above mentioned Manual 

 makes some concessions toward this idea by giving a list of 

 sixty-five forms which it recognizes as valid species. It is cer- 

 tain, however, that there are not even sixty-five species in the 

 sense that the older botanists recognized species, for they were 

 quite familiar with the plants of the region and would have 

 been sure to name at least the major part of the number in- 

 dicated. The fact is the modern race of botanists has not suc- 

 ceeded in discovering new species in places familiar to the 

 plant collectors of former days. What it has done is simply 

 to put together a new definition of species which will enable it 

 to name the varieties of the older botanists in a new category. 

 Under these conditions, it will not be surprising to find new 

 species being described in any genus. All that is necessary is 

 to make your distinctions fine enough and a crop of new spe- 

 cies is the inevitable result. This has been so in Antennaria, 

 Sisyrinchium, Pmiicum, Viola and many others, and the only 

 reason that every genus has not similarly expanded is because 

 no botanical segregator has attacked them. At the same time, 



