2o8 REPRODUCTION 



d. Value in Diagnosis. Lichen spermogonia have once and again 

 been found of value in deciding the affinity of related plants, and though 

 there are a' number of lichens in which we have no record of their occurrence, 

 they are so constant in others, that they cannot be ignored in any true 

 estimation of species. Nylander laid undue stress on spermogonial characters, 

 considering them of almost higher diagnostic value than the much more 

 important ascosporous fruit. They are, after all, subsidiary organs, and 

 often— especially in crustaceous species — they are absent, or their relation 

 to the species under examination is doubtful. 



