356 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



expert growers. Besides, after knowing the reasons for the methods 

 employed one may travel farther in the path of progress and attempt 

 many germinations that no one has known how to secure until now. 

 It can thus be foreseen that in the near future the growing of orchids 

 will receive a new impetus while the number of successes in cultiva- 

 tion will continue to increase, and new hybrids will become more and 

 more numerous. At the present time there are signs in the horti- 

 cultural world, especially in England and Belgium, that all the recent 

 discoveries have been appreciated; we hear of an unexpected number 

 of new floral offerings which indicate that the daring of the growers 

 is increasing daily. The flowers that are today the queens of fashion 

 are the Odontoglossums. The creations obtained from the represent- 

 atives of this genus are multiplied every day and the types like the 

 Odontiodas (the result of a cross between an Odontoglossum and a 

 Cochlioda) are the glory of the exhibitions. One would never sus- 

 pect that a venerable science like botany, apparently adapted only 

 for the delight of collectors who have a pleasant fancy for gluing 

 dry plants on paper, could be capable of affording such assistance to 

 an industry so important as that of orchid growing. It could not be 

 anticipated that the biology of these plants was so extraordinary. 

 They are, in short, plants that are normally diseased, which not only 

 accommodate themselves to their parasites but are unable to exist 

 without them. It may nevertheless happen that the latter take the 

 offensive and then the plant is Idlled. The struggle must be con- 

 tinuous between the fungus and its host, and in certain cases it hap- 

 pens that the resistance of the orchid is so strong that the mycorhiza 

 is completely digested and nothing remains at the end of this 

 violently defensive act but some excreta or the debris of half 

 atrophied threads. The reaction of the host under normal condi- 

 tion is always severe, and the phagocytose, which functions in a 

 regular manner, limits every day the threatened progress of the para- 

 site. It may be easily understood that such a struggle affects the 

 whole structure of the plant and that the normal characters of 

 orchids depend upon it to a large extent. The evolution of the 

 attacking organisms is analogous to that of those attacked. The 

 fungi separated from a Vanda are not the same as those found in 

 an Odontoglossum; they are parasites of the same family, but dis- 

 tinct specifically. One is tempted to believe that for each orchid 

 there is a corresponding fimgus specifically different from all others. 

 At present it appears that there is only a small number. Three 

 species clearly distinct have been described;^ one which inhabits 

 the roots of Cypripediums, Cattleyas, and Laelias ; another which is 



1 Burgeff admits that in every orchid there is a different species of fungus (Orcheomyces). 

 Burgeff. Die Wurzelpilze der Orchideen. Jhre Kultur und ihr Leben in der Pflanze. 

 Jena, 1909. 



