284 THE FLANT WORLD. 



fragmentary herbarium specimens. Even these are imperfect, 

 for all taxonomic characters are seldom shown by a plant at one 

 time. For instance, flowers and mature fruit are seldom found 

 together. 



To the uninitiated it is always questionable what to take note 

 on. What are the differences which these plants present one 

 with another? There never were better descriptions than those 

 of Dr. Engelmann, which are reasonably accessible. These usu- 

 ally characterize the plants fairly well and they can be relied 

 upon for a scale of points which should be noted. Color char- 

 acters are especially fugacious and these should be noted in the 

 field. This should include color of the general plant body, flower, 

 its parts, and the fruit. 



These plants are usually considered an epitome of variation, 

 but in spite of this, little space is devoted in any of our literature 

 to a characterization of this variation. Authors have generally 

 contented themselves with a description of the material before 

 them, which was often fragmentary, and we are therefore in 

 blissful ignorance regarding the limits of variation of any char- 

 acter in practically all of the species. That they are variable 

 there is no question, but I believe, after devoting considerable 

 time to a study of them for the past six years, that the variation 

 is of such a character that it can be defined. But this must be 

 done in the field. No amount of herbarium investigation will 

 do the work thoroughly, although laboratory studies and labo- 

 ratory materials are an indispensable adjunct. The study of con- 

 servatory living material often does not suffice, for there are 

 comparatively few of the species that grow normally in such 

 situations. Even when grown together out of doors some species 

 are perforce out of their natural environments and the forms are 

 often so modified as to be scarcely recognizable. I believe that 

 my confidence in my own sense of sight never received such a 

 shock as in connection with one of these plants out of its natural 

 habitat. It was on the coast of southern California under the 

 influence of the sea breeze that I found a specimen of Opuntia 

 fulgida, a plant perfectly familiar to me. When I asked Mr. 

 C. R. Orcutt, than whom few are better acquainted with this 



