MICHIGAN ACADEMY OF SCIENCE. 113 



of the mature trees. Enters bog areas soon after or actually with the bog 

 trees; is frequent as a rock shore pioneer. 



49. Thuja occidentalis L. Arbor Vitae; White Cedar. Common con- 

 stituent of the bog forest, especially where sphagnum is practically absent, 

 rarely where it is abundant; most characteristic tree of the delta swamp 

 forest; occurs frequently as a rock shore pioneer, often taking the "krumm- 

 holz" form; sparingly in the climax forest, usually near its edge. 



50. Juniperus communis L. var. depressa.Pursh. Low Juniper. Abun- 

 dant crevice plant upon rock shores, later becoming a constituent of the 

 heath mat; frequent upon bare burned ridges where rock shore conditions 

 are duplicated, and persisting into the burn forest stage. 



51. Juniperus horizontalis Moench. Trailing Juniper. Abundant rock 

 shore crevice plant, becoming the most important binding agent in the 

 formation of the heath mat. 



Typhaceae. Cat-tail Famih\ 



52. Typha latifolia L. Common Cat-tail. Sedge zone of Delta Swamp 

 Succession; shores of very sheltered coves. 



Sparganiaceae. Bur-reed Family 



53. Sparganium diversifolium Graebner. Bur-reed. Aquatic, Delta 

 Swamp Succession. 



54. Sparganium angustifolium Michx. Tobin's Harbor. 



55. Sparganium minimum Fries. Aquatic, Delta Swamp Succession. 



Najadaceae. Pondweed Family. 



56. Potamogeton natans L. Pondweed. Aquatic, Delta Swamp Succes- 

 sion. 



57. Potamogeton epihydrus Raf. Pool in bog: head of Siskowit Bay. 



58. Potamogeton alpinus Balbis. Delta stream : McCargoe's Cove. 



59. Potamogeton amplifolius Tuckerm. Delta stream; sheltered cove; bog 

 lake. 



60. Potamogeton heterophyllus Schreb. Frequent aquatic in sheltered 

 bays, bog lakes, and delta streams. 



61. Potamogeton heterophyllus Schreb. f. terrestris Schlecht. Very wet 

 places on sedge mat, Bog Succession; edge of Sedge mat. Delta Swamp Suc- 

 cession. 



62. Potamogeton praelongus Wulf. Sheltered cove: Hay Bay. 



63. Potamogeton perfoliatus L. Commonest pondweed in sheltered bays. 



64. Potamogeton zosterifolius Schumacher. Bog lakes and sheltered bays. 



65. Potamogeton obtusifolius Mertens and Koch. Delta stream: Mc- 

 Cargoe's Cove. 



66. Potamogeton fliformis Pers. Sheltered cove: Hay Bay. 



*67. Potamogeton pectinatus L. "Margin of Sumner Lake." Holt. 



68. Naias flexilis (Willd.) Rostk. and Schmidt. Bog aquatic: Sumner 

 lake. 



Juncaginaceae. Arrow Grass Family. 



69. Scheuchzeria palustris L. Sedge mat. Bog Succession. 



70. Triglochin maritima L. Sedge mat, Bog Succession. 



1.5 



