1915] 



MACDOUGAL — MODIFICATION OF GERM-PLASM 259 



the operator opportunity to preserve the original material 

 alive and to have it for comparison with succeeding genera- 

 tions. 



The numerous cacti in the vicinity of the Desert Laboratory 

 lead them to be selected for some tests, and the mechanical 

 conditions for operation which they offer are unexcelled. As 

 much as 1 cc. of solution may be introduced into the ovary of 

 an opuntia without traumatic effects, but as all are under 

 suspicion as to their genetic complexity, and as they germi- 

 nate and develop slowly, the investigator must wait the greater 

 part of a decade to obtain decisive results. Striking depart- 

 ures were obtained with Echinocereus Fendleri, a small cylin- 

 drical form native to southern Arizona, and the changed 

 characters grouped in one derivative have not been obtained 

 in nature or in cultures of the original. This derivative has 

 been obtained a second time. The species, however, presents 

 such a complexity of characters that definite conclusions are 

 difficult. 



Similar conditions were encountered in Penstemon Wrightii, 

 about which an announcement was made in 1909. Some of 

 these, however, furnished material from which the greatest 

 sources of error might be eliminated. 



The search for suitable subjects for experimentation was 

 continued and the results with Penstemon led to a closer ex- 

 amination of other members of the Scrophulariaceae. Finally, 

 an undescribed species of Scrophularia from the pine-forest 

 area on the Santa Catalina Mountains in Arizona was brought 

 into the environic series of the Laboratory of this Department 

 in 1909. Eootstocks were taken to the Coastal Laboratory, 

 and seeds were germinated at various localities. After hav- 

 ing seen many hundreds of plants taken from various parts of 

 its range and having followed them thoroughly two and three 

 generations, it was found that the species is a simple one and 

 not readily separable into elementary forms or strains. The 

 only noticeable feature suggestive of complications was the 

 fact that the broad-bladed nepionic leaf-forms are sometimes 

 carried nearly to the summits of stems grown under certain 

 conditions, giving the appearance of a robust race. 



