THE STANDPOINT OF BOTANY 63 



not perf onn their very important functions until 

 the cells are dead. Just how a group of dead 

 cells, performing a mechanical function, could 

 have been built up by Natural Selection, is hard 

 to imagine; and yet, in the case of the vascular 

 system its presence is a fundamental distinction 

 between two great divisions of the plant king- 

 dom. 



A striking illustration of the change of view 

 that plant structures are necessarily useful be- 

 cause they have been selected on account of adap- 

 tation has been developed by a very recent inves- 

 tigation of extra-floral nectaries,^ which included 

 an examination of 100 species of plants growing 

 in the Botanic Gardens of Buitenzorg, Java. 

 The view in reference to many of these extra- 

 floral nectaries has been that they attract ants, 

 which in turn defend the host plant from its ene- 

 mies. Hence we have such a category of plants 

 as myrmecophiles, or " ant-loving plants." Dar- 

 win himself naturally believed in myrmecophiles, 

 and Kerner included them among his illustrations 

 of protection against " unbidden guests." Now 

 it appears that any such use for these remark- 

 able organs is untenable; and there are many 

 facts that suggest that they have no definite pur- 

 pose that could be laid hold of as an adaptation. 

 The secretion often begins late in the life of the 

 plant, so that any protection it affords is lacking 



' Nieuwenhuis von Uxkiill-Giildenbandt, M.: " Extraflorale 

 Zuckerausscheidungen und Ameisenschutz," Ann. Jard. Bot. Bui- 

 tenzorg, II, 6; pp. 195-327. 1907. 



