22 THE WHITE PINE. 



Xurscry seoillings produce ntimerous slender, fibrous roots, the delicate tissues of which are as iu 

 most couilers easily dried at the time of transplanting, resulting iu very serious injury or loss of 

 plant material. White IMiies planted iipou the dry sand along the Lake Michigan 8h(ne and 

 trimmed of their lower branches have been observed restoring these lower limbs and forming a 

 thick, green covering over the roots betbre making any height growth, suggesting iu a striking 

 manner the necessity of protecting the root system against too rapid evaporation and a too highly 

 heated soil. In the natural forest, and in artificial groves jjrojjcrly planted, tin- fallen leaves fulfill 

 this function by making a deep, thick coating over the roots. 



LEAVES. 



The leaves arise from greatly reduced short branchlets and are produced five together, sur- 

 rounded at the base by a thin deciduous sheath, and are further distinguished by being more 

 slender and delicate than those of our other native pines. (PI. V, 7, :>, .5, i.) The relative jiosition 

 of the five leaves inclosed in their common sheath is shown in PI. V, 5, and in PI. V, (i, is repre- 

 sented a cross section of a single leaf, magnified sufficiently to show the characteristic arrange- 

 ment of the tissues. 



Without entering into a detailed account of its functions, which would here be irrelevant, it 

 may nevertheless be remarked that the leaf of the White Pine constitutes a highly coinjilicatcd 

 and delicate piece of apparatus. Like all foliage leaves, the leaf of the ^Vhite Pine fulfills the 

 important functions of respiration and the manufacture of starchy food, during which processes 

 large amounts of watery vapor are exhaled. 



A healthy pine seedling, three years old, iu the air of a dry room, lost by evaporation in 

 twenty-four hours 81.1 per cent and iu the following twenty-five hours 90.7 per cent of its entire 

 dry weight.' The evaporation, chiefly through the leaves, is more rapid in the daytime than in 

 the night, in clear than in cloudy weather, and most rapid of all in a drying wind. It will readily 

 be seen that if a tree is planted on a clear, dry, and windy day, the conditions are the most 

 unfavorable that could possibly be chosen, the rapid evaporation carrying oft' the water of the 

 plant beyond the capacity of the roots, not yet adapted to their new place, to meet the demand, 

 which results in the drying ui) of the tissues and often in the death of the tree. 



The various forms of modified leaves are chara(;terized by extreme delicacy. Winter buds 

 (PI. V, r\ with their thin and small scales, present a striking contrast to tho.se of Longleaf Pine, for 

 example, and other species tiiat produce large buds with relatively thick and coarse scales. The 

 very loose leaf sheaths and scale like leaves of the young shoots are early deciduous, a fact that 

 contributes to the growth of the smooth, clean bark characteristic of the branches of White Pine, 

 in which it differs in so marked a way from the sjjccies of the Yellow Pine group. 



In PI. V, 1, the modified, scale like leaves that constitute the loose sheaths are conspicuously 

 shown. Separate fascicles, with their sheaths, are represented in PI. V at 2 and 5, while at / is an 

 older one as it aitpears at the end of the summer after the sheath has fallen. 



EXPLANATION OK PLATE V. 



/. .Shoot sliowiiif; foliaj;e and sc.ili' le.ives of different ages. 



2. Voiuig fascicle with sheath. 



S. Young fascicle further developed. 



4. Still older fascicle from which the deciduous sheath has fallen. 



5. Section of fascicle inclosed in sheath. 

 G. Section of leaf uiiignitied. 



7. Wiuter hud. 



FLORAL ORGANS. 



Flowers and fruit are rarely produced to any considerable extent before the tree has attained 

 the age of fifteen or twenty years, though occasionally trees may bear fruit at ten to twelve years 

 of age. 



The stamiuate and i)istillate flowers are .separate, but ])roduced on the same tree. They 

 appear in Jlay, the pollen ripening and pollination taking place (in the latitude of Ann Arbor, 



' According to determinations made iu the botanical laboratory of the University of Michigan, November 18, 1886. 



