78 Standley : Some Echinocerei of New Mexico 



of spines in the areolae, length and color of spines, size and color 

 of flowers, shape of petals, length of stamens, number and color 

 of stigmas, and several less important details. These measure- 

 ments were continued as the different plants came into flower, 

 until a freeze the twenty-sixth of April killed all the flowers and 

 buds. On account of this freeze it was impossible to make any 

 study of the fruits, characters of which may be of value in separat- 

 ing the species. 



A number of species, all of them separable with difficulty, 

 have been named in this group of Echinocerei. After some 

 study of the type materials the writer decided that three reason- 

 ably distinct species were represented by the material in the 

 garden, E. polyacantJius Engelm., E. coccineas Engelm., and E. 

 conoideus Engelm. In order to facilitate a comparison between 

 these three species, after careful study of the plants as a whole, a 

 selection was made among the plants in the garden of one hundred 

 individuals to represent each of the three species. The plants 

 selected were those considered to be most typical of the species 

 and were easily separated from the others and from each other, 

 although there were many plants in the garden that it would have 

 been difficult to refer to any of the species with any degree of 

 certainty. Here there was obviously room for error, but this must 

 always be the case in any determination of species. These three 

 lots of plants are those hereafter referred to as E. coccineus, E. 

 polyacantJius, and E. conoideus. 



The measurements of these selected plants, together with the 

 measurements of the entire lot, were then tabulated and an attempt 

 made at a graphical statistical study of them. Curves were plotted 

 illustrating the variation in each lot and a comparison was made 

 of the four sets of curves in order to see whether any of the char- 

 acteristics exhibited by any one lot of plants were peculiar to that 

 species alone. The results were rather disappointing. Out of 

 the whole number of living plants studied it was impossible to dis- 

 tinguish more than four species, while any one glancing over the 

 plants and noting the great variation in color and size of spines 

 and flowers would have guessed that at least a dozen distinct 

 forms were represented. There is even some doubt whether at 



least three of these so-called species may not be forms of a single 

 species. 



