igisl /• Arthur Harris aiid Ross Aiken Gorfner 53 



The proliferous fruit of P. gracilis is characterized in the sim- 

 plest cases by the production, from the base of the fruit, of a stalked 

 whorl or series of whorls of incompletely closed carpels. In such 

 cases the prohfication must be regarded as morphologically a con- 

 tinuation of the axis, whose activity generally closes with the for- 

 mation of the carpels constituting the normal ovary. The included 

 or abnormal mass, as we shall sometimes designate this accessory 

 carpellary whorl, is generally large, green and turgid, but it may be 

 small and shrivelled. It may become so large as to rupture the 

 normal ovary wall. The Variation in structural details is very great 

 and will form the subject of a forthcoming memoir by one of us. 



The fruits which have furnished the materials for this paper 

 have been selected with great care as to morphological type. They 

 comprise exclusively those which are trimerous (the normal con- 

 dition, i. e., with six external sutures and three placentae) in the 

 Organization of their wall, and have a large living basal prolifica- 

 tion with an external whorl of four carpels. The diagrams (Plate 

 3) make clear the type of fruit dealt with. Numerous detail draw- 

 ings will be published when the morphological problems are taken up. 



2. Material. The materials upon which the constants were 

 determined were drawn from five cultures of P. gracilis grown 

 under slightly varying conditions on the grounds of the Station for 

 Experimental Evolution in the summer of 19 13. All the plants were 

 typical and (relatively) normally grown.^ These five series do 

 not include all of the fruits taken into consideration in our work, 

 but since the other experiments were made under highly abnormal 

 conditions of growth for special purposes, it seems quite legitimate 

 to leave them out of account here. 



Three of the cultures represent a strain which has been under 

 cultivation at the Station since the summer of 1908, when the seed 

 was secured from an American dealer. The second lot of seed 

 was a commercial sample bought from Haage und Schmidt, of 

 Erfurt. The series considered^ are : 



iP. gracilis is an exotic; while it grows magnificently in our latitude when 

 Started under glass, it is probably not quite legitimate to speak of normal con- 

 ditions of growth. 



2 All seeds were germinated under glass and transferred to 8 cm. pots 

 before planting into the garden. 



