9O ROBERT A. BUDIXGTOX. 



satisfactory manner; yet, they may all indicate precociousness. 

 Assuredly, one reflects that hastened specialization of tissues in 

 amphibian larvae, in dipteran larvae, in protozoa, were all accom- 

 panied by under-size; and Gudernatsch's ('15) experiments with 

 a mammal showed the same diminished size in his thyroid fed 

 line. 



The further question whether all protoplasm reacts, and reacts 

 similarly to thyroid components can hardly be answered, even 

 tentatively, while the amount of study of plant responses is so 

 small. Also, one can feel only the most limited concern whether 

 any special plant tissue is amenable to such hormones or not ; but 

 the more general inquiry as to the qualities of protoplasm as a 

 whole makes a real appeal. So far as the substance of this group 

 of observations goes, the evidence would seem to suggest an 

 affirmative answer. 



SUMMARY. 



1. Roots growing from bulbs of Narcissus into Pfeffer's 

 nutrient solution to which has been added certain amounts of 

 thyroid gland substance show a growth which is markedly 

 abbreviated as compared with that of the control lines. This 

 result is wholly like that when Allium is used. 



2. Measurements directed to find out the internal conditions 

 correlated with shorter growth indicate that differentiation of 

 the special root tissues extends nearer to the tip of the root in 

 thyroid "fed" lines than it does in the controls. 



3. Assuming that the tissues in freshly growing plant roots can 

 be compared to those in larval animals (Amphibia) both 

 originate from essentially unspecialized masses, although the 

 plant never reaches the complexity of the animal it would seem 

 that thyroid substances cause precocious differentiation in both. 



4. The suggestion is offered that animal and plant protoplasm 

 are sufficiently alike in their general physiology so that they 

 respond similarly to thyroid substances; or, expressed conversely, 

 thyroid substances are influential in essentially the same manner 

 on all protoplasm. 



LITERATURE. 

 Budington, R. A. 



'19 The Influence of Certain Ductless Gland Substances on tin- C'.rowth of Plant 

 Tissues. BIOL. BULL., 37, 3, 188-193. 



