REGENERATION IN PLANTS 89 



the apical part of a piece of the flowering plant. In this plant the 

 seeds ripen normally, presumably because of the migration of stuffs 

 toward the developing seeds. The results in all these cases are due, 

 Goebel thinks, to the direction of the flow of formative stuffs, and 

 cannot be explained as connected in any way with the limited 

 growth of the part. 



These cases, cited by Goebel, are not in my opinion altogether to 

 the point ; and they fail also to establish convincingly the conclusion 

 that Goebel draws from them. It may be granted that starch is 

 stored up in certain parts of the plant, and if these parts are re- 

 moved the starch may be stored up in other parts, as Vochting 

 ('87) has shown; but that the movement of this starch to the base 

 can account for the lack of development of the seeds in certain cases 

 seems to me improbable, or, at least, far from being established by 

 the cases cited. It may be granted that the presence of starch in a 

 region may act on the organs there present and determine their fate. 

 Vochting has shown in the potato that by removing the tubers the 

 axial buds, especially in the basal leaves, become tuber-like bodies, 

 but it should not be overlooked that the tubers themselves are formed 

 from underground stolons, that arise in the same way as do those 

 in the axils of the leaves. It would be erroneous, I think, to con- 

 clude from these cases of the effect of food stuffs on certain re- 

 gions that there are formative stuffs for all the organs of the plant, 

 and that these stuffs migrate in different directions and determine 

 the nature of the part. Even the migration of such substances in 

 definite directions in the tissue is itself in need of explanation, since 

 it has been made highly probable by Vochting's experiments that 

 this is not produced by agents outside of the plant. Furthermore, 

 Vochting has shown that the tendency of starch to accumulate in the 

 tubers and the formation of the tuber are separate phenomena. 



This hypothesis of formative stuffs held by such able botanists 

 as Sachs and Goebel demands nevertheless serious consideration, if 

 for no other reason than that if it is true it offers quite a simple 

 explanation of many phenomena of growth and of regeneration. We 

 should, I think, distinguish between specific or formative stuffs and 

 building or food stuffs. By specific stuffs is meant a special kind of 

 substance which, being present in a part, determines the nature of the 

 part. Sachs supposes, for instance, that a specific substance is made 

 by the leaves of a plant which is transported to the vegetative, growing 

 region (which has so far produced only leaves), and changes its 

 growth so that flowers are produced. Goebel does not commit him- 

 self altogether to specific stuffs of this sort, but speaks also of 

 building stuffs. By building stuff we may understand food material 

 that is necessary for growth, and from which any part of the plant 



