July 13, 1892.] 



Garden and Forest. 



335 



panied by moisture, and is thus never excessive or dangerous 

 for trees whicli naturally seelc the hijht. Tlie moisture and 

 heat combined produce a most vigorous and dense vegetation, 

 the very opposite to wliat is found in tlie arid zones. The 

 effort of tlie tree is tlierefore concentrated in its endeavor to 

 reacli tlie liglit and to push out from the dense sliade nearer 

 the ground. The most vigorous growing trees in this region 

 send up straight and undivided trunks to a level with the top 

 of the dense untlergrowth, branch at tliis level and form im- 

 mense umbrella-like crowns above less vigorous trees. This 

 umbrella form gives to the tropical landscape a distinct and 

 characteristic appearance. A tendency to assume such an 

 lunbrella form can also be recognized among those trees of 

 the temperate zone which grow in moist ])laces, such as river- 

 bottoms, canons cmd other sheltered localities — trees, in fact, 

 which delight in moisture. But nowhere is the form so pro- 

 nounced as in the tropics, where it is common with all large 

 species of the denser forests. The uplands of the tropics, 

 where the rainfall is less and where heat and drying winds are 

 more powerful, and where, accordingly, the vegetation is less 

 dense, the umbrella form is rare, or where it exists is caused 

 by other agencies. 



" The origin of the tropical umbrella form is, therefore, not 

 exactly identical with that of the umbrella form assumed by 

 most Pines in such districts as the Mediterranean or the Gulf 

 region of the United States, and, to a certain extent, also by a 

 few more northern Pines. This umbrella form is caused by 

 the falling off of the lower branches, which never possess the 

 strength of the upper limbs. The umbrella form, however, 

 greatly favors their struggle against wind and heat. 



" fn these drier places in the tropical districts the umbrella 

 form gives place to the globular form, the conditions there 

 being quite similar to what they are in the drier regions farther 

 north. Observe, for instance, the form of the Ceiba (Bombax 

 Ceiba), which inhabits drier localities in the Central American 

 tropics. This tree is almost globular in shape, in order that 

 its branches may give necessary shelter to the trunk and to 

 keep away the reflected heat. An effort to change the form 

 of this tree by pruning results fatally, as the branches become 

 sun-scalded and a prey to borers, which eventually destroy the 

 tree, hi crossing Central America I was especially impressed 

 by these different tree forms, characteristic of different regions. 

 Along the lowlands of the Pacific coast, up to 2,000 to 3,000 

 feet, the characteristic form of the various strong-growing 

 trees was the umbrella form. Above 3,000, and from that 

 altitude toward the interior in the dry and warm district, the 

 globular form predominates. As we ascend the interior high- 

 lands in the vicinity of Coban the climate suddenly changes 

 and becomes very moist. With this change comes also a 

 change in the form of the trees, which here assume the regu- 

 lar umbrella form. The same climate continues uninterrupted 

 to the Atlantic coast, and the district is characterized through- 

 out by the predominating umbrella form. 



"All trees require more protection when young, and this 

 explains why young trees are shaped differently from older 

 trees. Thus the form of a young specimen of the common 

 Blue Gum (Eucalyptus) is well known. While young the tree 

 is pyramidal, and the sloping branches are covered by hori- 

 zontally extended leaves. No form can be more adapted to 

 withstand heavy winds. As the tree grows older, the stem 

 stronger, and the roots penetrate deeper, this original form is 

 not required any more, and the tree assumes a semi-umbrella- 

 like crown. 



"tf we consider the principal forms of trees in their connec- 

 tion with influences of wind, snow, rain, sunshine and heat, we 

 find that the various forms may be grouped principally under 

 the following heads : 



"(i) The upright form, with a central undivided trunk and 

 with downward sloping branches. This form is possessed by 

 most conifers inhabiting snow-visited regions. The down- 

 ward slope of the branches facilitates the shedding of 'the 

 snow, while the undivided trunk offers less resistance to heavy 

 loads of snow. Forked or branched trunks would split or break. 



"This form may be either necessary to the species, as when 

 the latter is confined to snow-visited districts (example, Picea 

 amabilis), or it may be inherited and continue as a character- 

 istic of the species which grows in a warmer climate, but 

 which evidently had been evolved from a species which once 

 inhabited colder regions. Example : the Redwood (Sequoia 

 sempervirens), Lawson Cypress (Cupressus Lawsoniana) and 

 many other evergTeen trees inhabiting the moist, snowless 

 climate of the Pacific coast north of San Francisco. 



" (2) The upright form, with erect or horizontal branches. 

 The upright trunk in this form must be considered as inherited 

 from ancestors where it was a necessity. Later on the sloping 



branches gradually assumed a horizontal position. Example : 

 most species of Cypress, Yew, Juniper, etc., of a more southern 

 origin. It is interesting to note the form of Cedrus Deodara, 

 or Himalaya Cedar. This tree, growing in regions of Hima- 

 laya where heavy snowfalls are not infrequent, possesses 

 while young characteristically downward sloping branches. 

 C. Libani, Lebanon Cedar, which is only a form of C. Deodara, 

 possesses no such sloping branches, but horizontal branches, 

 evidently developed in a climate where the absence of heavy 

 snow has made the downward slope of the liranches unneces- 

 sary. Most species of Juniper possess erect branches, as 

 would be expected in a genus which finds its most congenial 

 home and greatest development in the warmer regions of the 

 Mediterranean, vvhci'e snow is almost unknown. 



"One species (Juniperus communis), however, which is 

 common in northern I^urope, is distinguished by a very differ- 

 ent form from the southern species, being dwarfed, prostrate, 

 and repeatedly branched. But that this form of the European 

 Juniper is not the natural one, can bo seen by the fact that 

 whenever this species is transferred to snowless localities it at 

 once assumes the upright form, growing as straight and slen- 

 der as a southern Cypress. Similarly we find this upright form 

 possessed by all specimens of this Juniper which grow in close 

 proximity to smelling works, where the heat is strong enough 

 to melt the snow. The different appearance of this Juniper in 

 such localities is really most startling. 



"Pines which inhabit snow-visited regions are, as a rule, 

 very upright, with downward sloping branches, while the 

 southern Pines, both in Europe and North America, as well as 

 in Central America and Mexico, have branches which either 

 spread horizontally or which stand erect. Compare, for in- 

 stance, P. Lambertiana and P. Cembra, which inhabit snow- 

 visited regions, with such species as Aleppo Pine (P. Halapen- 

 sis), P. maritima, P. insignis and P. Sabiniana. Judging by the 

 forms of most species of Pines, it would seem as if this genus 

 is more of a southern origin than, for instance, the various 

 genera of Firs and Spruces which, through their very charac- 

 teristic undivided stems and sloping branches, indicate their 

 origin in the snowy regions in the north. 



"(3) The globular form. This form is possessed by trees in 

 warm and dry regions or localities. The object of the form is 

 to protect the tree from sun and heat and to preserve the 

 moisture in the soil around the root. Example : the Live Oak, 

 the wild California Walnut, the Texas Umbrella and the trop- 

 ical Ceiba, or Bombax-tree. The Mesquite of the Mojave 

 Desert belongs to this form. 



"(4) The umbrella form. This form is principally found in 

 moist tropical climates. The object of the form is to give to 

 the tree as much sun and heat as possible, which can again 

 only be had at a certain altitude above the tops of the dwarfer 

 vegetation. Example : various papilionaceous trees, as well 

 as most varieties of trees in the tropical lowlands of both con- 

 tinents. 



" In connection with this, I will call attention to the form of 

 the bases of the trunks and of the surface-roots in trees grow- 

 ing in moist places, especially in the tropics. The trunks 

 branch out above the soil and form peculiar horizontally com- 

 pressed roots, sometimes five to six feet high, but only a few" 

 inches thick. Such surface-roots are found in most tropical 

 trees, as well as in many swamp trees ; forinstance, the Swamp 

 Cedar of the Mississippi delta. The object is to steady the tree 

 when floods or excessive rains soften the ground ; round roots 

 would then offer much less resistance." 



Notes. 



Excellent peaches from Georgia are now offered on all the 

 fruit-stands of this city. 



Dr. Ignatius Urban has just issued in separate form his 

 Additamenia ad Cognitionem Flora Indies Occidoitalis from 

 the fifteenth volume of Engler's Botanischer Jahresbericht. 

 It contains descriptions of new Antillian species, with critical 

 notes on others, based principally on recent exploration in the 

 West Indies. 



What promises to be a work of much value to the many 

 horticulturists in America who read German is the recently 

 announced Forsliche Botanik (Forest Botany), of Dr. Franz 

 Schwarz. It will be published by Paul Parey in Berlin, will 

 form a large octavo volume illustrated by two plates in photo- 

 gravure and 456 wood-cuts, and will be sold for 15 marks. 



On the roof of the New York State Building, in the World's 

 Fair-grounds at Chicago, which is to be built by Messrs. 

 McKim, Mead & White, three terraced gardens will be ar- 



