122 



The Michillinda (Michigan) Sand Dunes and Their Flora. 



Stanley Coulter. 



Nowhere is the struggle for a place in nature by plants more spectacular 

 or more severe thau that with the saud dunes. The alignment of the op- 

 posing fox'ces is so evident, their acti^■ity is so ceaseless, their modes of at- 

 tack so varied that one wonders that the plants ever succeed in fixing these 

 restless masses of sand. After the classic studies of Cowles upon the Dune 

 tlora it would seem that little remains to be said, but to the botanist accus- 

 tomed to the placid plant life of mesophytic regions the struggle is irresist- 

 ibly fascinating and, as a rule, he is unable to resist the temptation of a 

 new consideration of soine phases of the problem. 



The region studied was a short stretch of beach dunes on the east shore 

 of Lake Michigan at a summer resort known as Michillinda, about twenty- 

 five miles north of Muskegon. That the region is exceptionally favorable 

 for such studies is evidenced by the fact that it is the place chosen by Dr. 

 Cowles for his classes when considering the problems presented by the 

 dune flora. The study made was neither systematic nor exhaustive; it was 

 merely a part of a I'est of three weeks after a summer school session. No 

 attempt was made to enumerate the constituent members of the flora or to 

 work out all of the factors determining the success or failure of the plant 

 invaders. The paper, therefore, touches only the more evident features of 

 the problem and treats even these in the line of suggestion rather than ex- 

 planation. 



The plants begin their struggle on what Cowles calls the middle beach, 

 a region beaten by the winter waves, but as a rule dry during the summer 

 months. The struggle here is almost hopeless and on the open stretches of 

 the beach the plants are extremely scattered. In the shelter of the drift 

 logs and debris, however, they are more numerous and may maintain a 

 precarious existence for some months. It is probably the area of greatest 

 stress. The fierce winter storms compel an absolute renewal of the struggle 

 each succeeding year, while the summer winds and sun make it possible 

 for only such plants as possess the most marked xerophytic characters to 

 maintain themselves. A severe summer storm may overwhelm the beach, 



