HioNRY AND Flood — The Dotiglm Firs. 85 



for contingencies such as damage from wiml, insects, etc , estimates the yield 

 resulting from plaiiliiig land of average (iuality with tliis sjjccies to he 7000 

 cubic feet at the end of sixty years. The early maturity and great volume 

 of the Oregon Douglas Fir make it the most profitable tree to employ in 

 afforestation schemes. 



The Oregon Douglas Fir has certain disadvantages, and should only be 

 planted in carefully selected areas. It suffers much from exposure to strong 

 prevailing wind, and does not thrive in wet land or on heavy clay or gravelly 

 soils. It has an aversion to lime diffused in the soil ; but nevertheless makes 

 considerable height and girth on chalk and limestone that are covered with a 

 surface layer of humus, in such cases forming wide-spreading superficial 

 roots. It is liable in the young stage to injury from spring and autumn 

 frosts. These drawbacks limit considerably the area in which it can be 

 commercially planted. It is a splendid tree in sheltered situations where the 

 soil is moderately deep and not too wet. When not exposed to wind, it 

 grows well enough at high elevations; plantations in Wales being successful 

 in favoured spots np to 1250 feet. At Garmaddie, Balmoral, a plantation at 

 1100 feet attained in twenty -six years a height of 45 to 50 feet. 



While attaining its maximum development on deep loamy sands, it 

 thrives much better on poor sandy soils than is generally supposed. This is 

 an important fact, as it renders proHtable the affoi'estation of large tracts of 

 poor heath land in England, which would yield only a slight return if planted 

 with any other species or if put under the plough. In such soils it often 

 establishes itself with difficulty, and looks yellow in foliage for a time ; but 

 this is generally a passing phase. Thus at Westwick, Norfolk, on poor 

 sandy heath, where Larch and Scots Pine do not exceed in the best spots 

 60 feet high at eighty years old, plantations of Oregon Douglas Fir, that 

 looked unpromising at first, are now very thriving, and average 40 feet in 

 height at twenty years old. In Holstein, poor heath land,i on which Scots 

 Pine and Spruce were subject to root-rot and failed, was successfully afforested 

 with Oregon Douglas Fir, which in thirty years has grown to timber size. 



IV. — Anatomy of the Leaf. 



The microscopical structure of the leaf has proved useful in tlie dis- 

 crimination of species in various genera of conifers, notably Abies- and 

 Pinus.^ In a paper lately read before this Academy, we found the leaf 



' Trans R. Scott. Arbor. Soc, xxii, 235 (1009). 

 = M'Nab, in Proc. Roy. Irish Acad., ii, 073 (1870). 



'Masters, ia Journ. Linn. Soc. Bot., xxxv, 50U-659 (1904). and Sliaw, The Genus 

 Finns (1914). 



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