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A Chemico=Physiological Study of Spirogyra 



nitida. 



By Mary Engle Pennington, Ph.D. 



Research Fellow in Botany. 



AS the physiologist investigates more and more mi- 

 nutely the problems of plant life, he is confronted 

 on every hand by chemical questions, to many of 

 which he can still give no answer. The pharmacist has 

 introduced us to a great variety of substances obtained 

 from vegetable sources, but he has told us nothing of 

 their origin or use in the plant economy. 



Together the chemists and physiologists, working in 

 this field, are little by little surmounting the difficulties 

 which beset the path leading to our more perfect under- 

 standing of the complex results as we find them in plant 

 life. It was with the hope of adding a few additional ob- 

 servations to our knowledge of chemico physiology that 

 the following investigation was undertaken. 



Spirogyra nitida was selected for this work because of its 

 quick response to stimuli and because of its simple struc- 

 ture. A considerable quantity of easily accessible and un- 

 usually pure material which appeared in a pond in the 

 Botanic Garden of the University of Pennsylvania made 

 the selection possible. 



By far the greater share of the knowledge which we pos- 

 sess of the laws of growth has been derived from a study 

 of the higher plants, where we have a division of labor. 

 • In this simple alga each cell functions, so far as we 

 have observed, as an independent organism, building up 

 the necessary compounds for its maintenance and giving 

 >~ off its waste products. The study of such simple forms 



CD 14 2 ° 3 



