6 BURSA BURSA-PASTORIS AND BURSA HEEGERI '. 



which show samples of three families which bred true to rather strikingly 

 distinct characters in his cultures. To these several forms he assigned 

 trinomial names, though no adequate description is given. No statement is 

 made as to the extent of the cultures upon which their standing as perma- 

 nent biotypes is based, nor is there any statement as to the extent and nature 

 of the fluctuating variability of each of the forms figured. Until attention 

 is given to such matters by the student of pedigree -cultures it will be im- 

 possible to properly estimate the security of conclusions drawn, or to rec- 

 ognize with any certainty the identity of biotypes discovered by different 

 investigators. 



To obviate these difficulties, I wrote to Dr. Lotsy for pedigreed seeds of 

 his several types, in order that they might be grown beside my own for the 

 purpose of testing their identity, but received the reply that none were 

 available. The questions as to whether Lotsy 's names are therefore to be 

 considered nomina nuda and whether I am justified in assigning new names 

 to the biotypes to be discussed below, which may or may not be identical 

 with one or more of Lotsy 's named elementary species, I leave to the tax- 

 onomist to decide. Indeed, in adopting the names used in this paper I have 

 been governed entirely by the demands of present utility and not by any 

 thought that these names will be accepted by taxonomists as having proper 

 standing in the nomenclatorial system now recognized by them. 



Still more recently, Almquist (1907) has published over 70 named " ele- 

 mentary species" of B. bursa-pastoris , but these are described in rather 

 general terms, and the cultures were conducted in the open garden un- 

 guarded, usually for but 2 to 4 generations. Almquist states (p. 5) that 

 after this length of time the cultures had either died out or were no longer 

 pure. He assumes that this " loss of purity " is due to vicinism with the 

 other elementary species growing on neighboring plots, and some of it 

 doubtless was. In my own cultures I have observed that some of the dif- 

 ferentiating characters used by Almquist disappear upon continued breed- 

 ing, even when vicinism is carefully excluded. It seems that members of 

 the same biotype coming from different habitats may retain certain fluctu- 

 ating" differences, such as differences in texture of leaves, degree of redness 

 of veins, degree of epinastic growth in the petioles, etc., for several gener- 

 ations of uniform treatment, but finally merge into identical forms, even 

 when crossing with other biotypes is entirely precluded by careful guarding. 



While I can not say with certainty that any of Almquist 's "elementary 

 species" are not distinct and permanent types, my experience indicates 

 emphatically that he has not demonstrated that they are. I think it very 

 probable that a number of the elementary species figured and described by 

 him will not stand the test of longer culture under more carefully controlled 

 conditions. However this may be, it seems evident that the number of 

 elementary species of Bursa may be considerable. At the time of the first 



