22 THE WHITE riNE. 



Nursery sciMlliiif^s inoiliice munerous slender, libioiis roots, tlie delicate tissues of which are as in 

 most <!oiiiteis easily dried at the time of transplanting, resulting in very serious injury or loss of 

 plant material. \Vliit<' Pines ])lanteil upon the tliy sand along the T^ake Michigan shore and 

 trimmed of their lower branches ha\ e been observed restoring these lower limbs aiid forming a 

 thick, green eoveriug over the roots before making any height growth, suggesting in a striking 

 manner the necessity ofi)rotecting the root system against too T'ajtid evai)oration anil a too highly 

 healed soil. In the natural forest, and in artihcial groves jiroix-rly planted, the falhui leaves fnllill 

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



LEAVES. 



The leaves arise from greatly reduced short branchlets ami 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. (IM. V, 1,~',o, J.) The relative iiositiim 

 of the live leaves inclosed in their common sheath is shown in PI. V, 5, and in I'l. \, C, is repre- 

 sented a cross section of a single leaf, magnified suflBciently 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 com]tlicated 

 and delicat«' piece of apparatus. Like all foliage leaves, the leaf of the White Pine fulfills the 

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

 large amounts of watery vajtor are exhaled. 



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

 twenty-four hours 81.1 per cent and in tlie following twenty-five hours 9(i.7 i)er cent of its entire 

 dry weight.' The evajioration, ehietly 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 evai)oratiou carrying otf the water of the 

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

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



The various forms of modified leaves are characterized by extreme delicacy. Winter buds 

 (PI. Y, ; ), with their thin and small .scales, present a striking contrast to those of Longleaf Pine, for 

 example, and other species that i)roduce laige buds with relatively thick and coarse scales. The 

 very loo.se 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 s])ecies of the Yellow Pine group. 



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

 shown. Separate fascicles, with their sheaths, are represented in PI. Y at 2 and 3, while at 1 is an 

 older one as it ai)])ears at the end of the; summer after the sheath has fallen. 



KXei.ANATlON OK PLATE V. 



/. Shoot showiiifi; f(iliiij;c and scale leaves of dilt'erenf ages. 



2. Voiiii}; faseiele with sheath. 



3. Yoniig faseiili: liirtlier ileveloi)c<l. 



•/. .Still oilier faseiele from which the cleciiliiiiiis sheath has fallen. 



5. Section of fascicle inclosed in sheath. 



G. Section of leaf niagniticd. 



7. Winter bud. 



FLORAL ORGANS. 



Flowers and fruit are rarely produced to any <!onsiderable extent before the tree has .attained 

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

 of age. 



The starainate and pistillate llowers are separate, but produced on the same tree. They 

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



' According to deleriuinatious made in the botanical laboratory of the University of Michigan, November 18, 1886. 



