CONTINENTAL NOTES — FRANCE. 47 



IV. We find in a Norwegian Manual of Silviculture by Barth 

 a quotation from another author, to the effect that the limit of 

 existence of forest species is fixed by the mean temperature 

 of the four months of vegetation, June to September. Thus, 

 birch (or at least Betiila odorata) is content with a mean summer 

 temperature of 45° F., the aspen and the white alder just under 

 46° F., Scots pine and spruce, 47° F., Aluus glutinosa, 54° F., the 

 oak just under 55° F., and the beech 56° F. In Norway 325 

 feet of altitude corresponds to a reduction in temperature of 

 just about i' F. These figures should be useful when planting 

 on mountain sides. 



We read also that for success in plantation the seed used 

 should not come from a locality of which the mean temperature 

 differs by more than 2-2° F. from that of the place concerned. 

 There are probably few who consider this, or who, if they did, 

 would confine themselves within such narrow limits. 



V. We read in Hickel's new book, Graines et plantules, 

 useful information concerning acorns. Those which fall early 

 are generally attacked by an insect {Balanimis), and are useless. 

 The acorns which adhere firmly to the cup are useless, being 

 unripe. However, after a drought acorns sometimes fall early 

 and are good. Except in this case, September acorns will 

 be no good. Acorns cannot be kept beyond the following 

 spring. The chief thing to be avoided, when storing them, is 

 excessive dessication. A crinkled pericarp, and one within 

 which the nut moves, means bad seed. Acorns do well if kept 

 under running water, or water which is often changed. They 

 will keep well in airy and dry places, provided the temperature 

 is low. A cellar would do well. Sometimes acorns can be 

 successfully kept in what would amount to a silo, under straw or 

 dry leaves covered with earth. In this case the radicle may 

 emerge, but — if the author has been correctly understood — the 

 fact that this will get broken as soon as the acorns are removed 

 for sowing is not a disadvantage, but the reverse, as it results in 

 an abundant production of root hairs. The best way to test the 

 quality of acorns is to cut them. If they cut easily and cleanly, 

 and do not jump under the knife, they are good. The cut 

 surface must be white or yellowish. The idea that a big acorn 

 is worth more than a small one has nothing in it. It has never 

 been shown that a plant from a small seed is, in any given 

 species, inferior to one from a large seed. 



