THE INFLUENCE OF THE LEAF 69 



explain how the sap sent out by a leaf can be separated into two 

 chemically distinct masses, one to travel in an ascending the other 

 in a descending direction in the stem. The writer is not aware 

 that such an assumption is justified on the basis of our present 

 knowledge. 



Slender stems with 5 nodes (designated as 0, 1, 2, 3, and 4) 

 were cut out from plants almost but not quite one year old. 

 All the leaves were removed except the pair of leaves in the third 

 node (Fig. 52). The stems were split longitudinally between the 

 two leaves, one leaf being left in connection with its half stem 

 (I, Fig. 52), while the other leaf was detached and suspended with 

 its apex dipping into water (III, Fig. 52). The two half stems 

 I and II dipped also with their base into water. Half stem I, 

 with a leaf attached in node 2, produced larger shoots at the apex 

 than the other half of the stem II with no leaf. The difference 

 in root formation was in the same sense and still greater. The 

 experiment lasted from Oct. 18 to Nov. 9. Six half stems with- 

 out leaves (II, Fig. 52) produced 28 milhgrams dry weight of 

 shoots, while the other six half stems each with a leaf produced 

 (during the same time under equal conditions) 237 milligrams 

 dry weight of shoots. Of this quantity about 209 milligrams were 

 therefore furnished by the leaves. The 6 isolated sister leaves 

 (III, Fig. 52) produced 292 milligrams of shoots. Hence more 

 than two-thirds of the material available for shoot formation 

 in the leaf was used for shoot formation in the apex of the stem. 

 The 6 isolated leaves produced 102 milligrams dry weight of 

 roots while the 6 half stems with leaves attached produced 136 

 milligrams. Hence the total quantity of regeneration in the 

 stems was 373 milhgrams, while the total quantity of regeneration 

 in the isolated leaves was 394 milhgrams. This shows that 

 the regeneration in the stems was determined chiefly by the sap 

 sent out by the leaves; the leaves in connection with the stem 

 produced neither roots nor shoots. 



The pieces of half stem without leaf had just commenced to 

 produce a few roots. It may be well to make use of this fact to 

 point out that the influence of the leaf on the root formation in 

 the stem cannot be ascribed merely to water being sent by the 

 leaf into the stem, since in this experiment stems both with and 

 without leaf (I and II, Fig. 52) were each placed with their base 

 in water, so that the stems without leaves had all the water they 

 needed for root formation at the base; yet their root formation 



