ECOLOGY OF NORTHERN MICHIGAN. 87 



9. Lycopodium complanatum L. In the alder thickets along Washington 

 river, II. and with the heaths on the Minong Trap promontory, IX. 



Isoetaceae Underw. Quillwort Family. 



* 10. Isoetes sp. Among the rocks in shallow water about the islands in 

 Lake Desor, VII. 



Pinaceae Lindl. Pine Family. 



11. Pinus strobus L. White Pine. Large isolated trees occur scattered 

 through the forest, III, and VI. Young trees occur on the jutting promon- 

 tories on the southwestern end of the island, IX. A few trees also occur 

 with P. resinosa on a small strip of rock beach on the north shore of Lake 

 Desor, VII. 



12. Pinus resinosa Ait. Norway or Red Pine. Large trees occur occas- 

 ionally in the coniferous forest on exposed slopes, VI. A few trees were 

 also found on the rocky promontory, IX, and with P. strobus on a small 

 strip of exposed beach on the north shore of Lake Desor, VII. 



13. Larix laricina (Du Roi) Koch. Tamarack. Occurs along the 

 flood-plains of the streams, where the valleys are broad, II, IV. It becomes 

 more abundant in bogs, forming a nearly pure stand, V. Also occurs occas- 

 ionally in the old beach pools on the Minong Trap promontory, IX. 



14. Picea canadensis (Mill.) B. S. P. White Spruce. Generally dis- 

 tributed. It occurs with the Tamarack and Black Spruce on the flood- 

 plains, II, IV, and forms an important part of the coniferous forest of the 

 slopes, VI, but becomes less abundant toward the top of the higher ridges, 

 III. With the Balsam Fir and Paper Birch, it succeeds the heaths and 

 Arbor Vitae on the rocky promontories, IX. 



15. Picea mariana (Mill.) B. S. P. Black Spruce. This tree is associated 

 with the Tamarack and White Spruce on the flood-plains of the streams, 

 II, IV. It also occurs occasionally in the old pools on the Minong Trap 

 promontory, IX. 



16. Abies balsamea (L.) Mill. Balsam Fir. This tree is generally dis- 

 tributed, occurring in the river valleys, II, IV, and on the ridges, III, VI. 

 It apparently forms, with the White and Yellow Birch and White Spruce, 

 the principle forest of the island. 



17. Thuja occidentalis L. White Cedar. Arbor Vitae. This tree is 

 most abundant in the valleys along streams, IV, where it occasionally forms 

 dense growths. It is also found, however, on the shores of Lake Desor, 

 VII, and about Washington Harbor, X; while on the Minong Trap promon- 

 tory, IX, it is the first tree to gain a foothold, and may be seen growing in the 

 crevices, nearly prostrate on the rock. 



18. Juniperus nana Willd. Low Juniper. Common on the rock surfaces, 

 of the Minong Trap promontory, IX. 



Taxaceae Lindl. Yew Family. 



19. Taxus canadensis Marsh. Ground Hemlock. This is one of the 

 most characteristic forms of the Isle Royale forest. It forms a dense and 

 almost impenetrable undergrowth throughout the coniferous woods, VI, 

 but it is not as abundant in the flood-plain societies, II, IV. In the bogs 



- it may be nearly or entirely wanting, and in the deciduous forest along the 

 top of the Greenstone Range, III, it is often replaced over small areas by 

 Cory I us rostrata. 



