xvi Minnesota Plant Life. 



FIG. 63. A patch of spore-cases on the back of a common polypody- 

 fern-leaf. Magnified. After Atkinson 170 



FIG. 64. Spore-cases of the common fern, much magnified, showing 

 how the spring back reverts and then snaps shut again, 

 throwing the spores as from a sling. After Atkinson 171 



FIG. 65. A walking-fern climbing down a hillside. Buds form at the 

 very tips of the slender leaves and grow into new plants. 

 After Atkinson 1 72 



FIG. 66. Maiden-hair ferns and lady ferns. After photograph by Wil- 

 liams 173 



FIG. 67. A fruiting stem of the horse-tail. The shield-shaped spore- 

 bearing leaves are aggregated in a cone. After Atkinson.. . . 176 



FIG. 68. Scouring-rush spores; to the left a spore with appendages 

 curled up, in moist air; to the right a spore with appendages 

 extended, in dry air. After Atkinson 177 



FIG. 69. Diagram of an ovary, with one seed-rudiment, in a higher 

 seed-plant, s, the stigma, where two pollen-spores have 

 germinated; o, wall of ovary; f, stalk of ovule; ai and ii, 

 rudimentary seed-coats; n, spore-case, with single large 

 spore, which has germinated to produce the reduced female 

 plant; k, the egg; e, the body which forms the albumen; b, 

 other cells of the female. The male plant is shown as a tubu- 

 lar thread growing towards the egg. After Atkinson 181 



FIG. 70. White pines on the rocks at Taylor's Falls. After photograph 



by Williams 187 



FIG. 71. Jack pine. After Britton and Brown 188 



FIG. 72. Rock-vegetation near Duluth. White pines, white cedars and 



junipers. After photograph by Williams 189 



FIG. 73. Tamarack swamp with sedge border. After photograph by 



Williams 191 



FIG. 74. Red cedars on the banks of a Minnesota lake. After photo- 

 graph by Williams 193 



