OF ENVIRONMENT 135 



as to the mechanical action of the reagents, and 

 with plants offering an ovarial structure most 

 difficult to deal with. In the development of the 

 method, non-corrosive syringes of glass with gold 

 needles and an extended list of substances were 

 employed, while a selection of species was made 

 in which the reagents could be brought into con- 

 tact with the egg apparatus with proportionately 

 least damage to its somatic structures. The sub- 

 stitution of dyes for the substances to be used 

 was found useful in making out the mechanical 

 results of an injection. Since these operations 

 inevitably resulted in the destruction of a large 

 number of ovules, it was found most convenient 

 to work with forms which are characterized by 

 many-seeded ovaries. By this development of 

 technique, more important results capable of def- 

 inite analysis were secured and a fair basis for a 

 theoretical explanation gained. 



Many progenies representing genera in widely 

 separated f amihes are now under observation, but 

 announcement of results beyond those of a year 

 ago will be confined to Penstemon. 



Penstemon •wrightii is a species well marked 

 and readily separable from its nearest relatives, 

 which alone of the genus inhabits the slopes 

 around the Desert Laboratory. It is, therefore, 

 growing under perfectly undisturbed conditions. 

 Various injections of zinc, calcium, and iodine 

 into the young ovaries were made when these 

 structures were not more than 3 mm. long and 



