8 



The Canadian Fik'.d-Naturalist 



[Vol. XXXIII. 



sugar ofl the trees, and patches of recrystalized sugar 

 may then be found at the base of trees or on the 

 ground. Frequently, however, in this situation it 

 daes not recrystalize but may be found in a fluid 

 or semi-fluid condition which is attractive to flies 

 and other insects. Sometimes, as above mentioned, 

 insects feed on the sugar while still on the trees, and 

 it is reported that bears go af^cr it, causing the 

 breakage of many branches. 



EXUDATIONS BY OTHER PLANTS. 



A.s is well known, many plants have structures 

 known as walerpores,, situated usually at the tip 

 or apex of the leaves, and, in the case of lobed 

 leaves, often at the tips of the lobes or teeth along 

 the margin. Occasionally when the root-pressure is 

 very active, so much water is forced up into the 

 plant that the leaves become gorged witli water 

 which escapes through these water-pores compar- 

 able to a kind of safety valve. Most people are 

 familiar with the drops of water at the tips of 

 grass leaves in the morning after a hot dry summer 

 day and a cool, clear night, giving origin to the 

 Scotch saying, "Ilka blade o' grass keeps its ain drap 

 o dew . 



In some localities, where the soil is calcareous, 

 minute white incrustations of lime are found around 

 the water-pores; ihese incrustations may be found on 

 grasses, and are of common occurrence on certain 

 species of Saxifrages which show them on every 

 tooth along the margin of the leaves, such incrusta- 

 tions are small, and are only formed under certain 

 ecological cond tions, in which temperature of the 

 soil and atmosphere, and water content of the soil 

 are important factors. 



FACTORS INFLUENCING EXUDATION OF SUGAR. 



A review of the disfributicn, and various factors 

 influencing the prcduction of sugar by Douglas fir, 

 will prove of especial interest to physiological and 

 ecological botanists, to whom the phenomenon will 

 serve as a splendid illustration of the influence of 

 environment en a plant which under ordinary con- 

 ditions in Bntish Columbia does not exude sugar. 

 DISTRIBUTION. 



The region in which sugar-bearing Douglas firs 

 are most abundant, lies between the 50th and 51st 

 parallels and between 12l-122 long. This in- 

 cludes the driest and hottest part of the dry-belt of 

 British Columbia. Within this area they are rather 

 common in the Thompscn valley west of the mouth 

 of the Nicola river, also near the junction of the 

 Thompson and Fraser rivers at Lytton ; they have 

 been found a little above Lilloet in the Fraser 

 valley, but according to present information are not 

 known to occur north of Clinton in this region. 



About 10 miles north of the apex of the angle 

 formed by the junction of the Thompson and 



Fraser rivers, lies Betani valley, at an altitude of 

 between 3,500 and 4,000 feet, some years sugar is 

 comparatively abundant on trees in this region; the 

 geology and flora is very different from that of 

 the adjacent Thompson or Fraser valleys; here one 

 may find sugar-bearing Douglas firs growing on the 

 southern and south-western slopes having the great- 

 est sun exposure. The soil produces a thick cover- 

 ing of grass and other vegetation, indicating a plenti- 

 ful supply of available soil moisture; differing in 

 this respect from the dry gravelly southern and 

 south-western slopes of the main valleys of the 

 Fraser and Thompson. 



Suitable habitats are found at intervals over a 

 considerable area of the dry-belt regions, in ad- 

 dition to samples received from the north and south 

 sides of the Thompson river near Spence's Bridge, 

 Douglas fir sugar has been reported from around 

 Kamloops and Savona, also from the Nicola and 

 Similkameen valleys, and is said to be found in the 

 southern part of Okanagan valley. In-so-far as the 

 chief of the Kootenay Indians is aware, it is not 

 known in the Kootenay country although it is re- 

 ported by an Indian as being found in eastern part 

 of Washington state. United States. 

 HABITATS. 



The habitats in which sugar-bearing firs are 

 found, are usually on gentle slopes facing east or 

 north in that region of the dry-belt where the Doug- 

 las fir is encroaching on the dry-belt flora. The 

 trees are in comparatively open areas with abund- 

 ant exposure to the sun. 



SOIL MOISTURE. 



As a rule, sugar is not found on trees situated 

 on fully exposed southern or western slopes, nor on 

 areas where Douglas fir forms a dense forest. 

 Southern and western slopes, exposed to the full heat 

 of the sun, dry cut much sooner than ground gently 

 sloping to the east or north; the greater abundance 

 of soil mcisture in the latter is a point to be kept 

 in mind. 



ABUNDANT SUNSHINE. 



In the region above mentioned the descending zone 

 of the Douglas fir and the ascending zone of yellow 

 pine overlap, so that the trees are well exposed to 

 the sun, not being so crowded as to limit the foliage 

 to a narrow crown, as happens in dense forests. An 

 abundance of leaves exposed to the sun will result 

 in an abundant formation of carbohydrates during 

 the day; under ordinary conditions these carbohy- 

 drates would be removed from the leaves and trans- 

 ported to growing tissues or storage tissues during 

 the night. This normally takes place in most plants, 

 including Douglas fir in its natural habitat in the 

 coast area where it forms dense forests of gigantic 

 trees. 



