KNOWLEDGE. 



January. 1911. 



will induce leaf-fall much as does a frost, and that a 

 laver of cork is formed below the prickles on old 

 stems of rose or bramble, and below twigs in some 

 plants which shed these branches as others shed their 

 leaves. On the other hand, if a branch be broken 

 through earh" in summer, its leaves wither but do not 

 fall, no absciss-laver being formed. Coppiced oaks 

 or the clipped beeches and hornbeams in the hedges 

 of nurserv-gardens also retain their leaves, as if the 

 energy- and material used up in the formation of 

 callus to heal the wounds caused by pruning-knife or 

 shears left none for the formation of the usual absciss- 

 la_\-ers. The pollard hornbeams of Epping Forest. 

 which used to retain their withered foliage through 

 the winter, have, since the Forest was taken over by 

 the Corporation of London, and lopping has been 

 stopped, been gradually regaining the deciduous 

 character of "spear" trees. 



Ever\-one must have noticed the successive fall of 

 the leaflets and the leaf-stalks in the ash or horse- 



chestnut, tlie thick-ended petioles being aptl\- known 

 b^" children as " bones." since they are b\- no means 

 unlike the leg-bones of birds. There is, however, 

 another interesting little point in connection with 

 leaf-fall which is, perhaps, less familiar, and which is 

 well illustrated in the photographs, by Mr, Johnson, 

 of Tunbridge \\'ells, from which our blocks have 

 been prepared. This is the order in which the 

 leaves fall from the twig. In the beech this is 

 hasipefal, i.e., the \ounger leaves at the apex of the 

 twigs fall first. In the linden, the poplar, and 

 apparenth" in the majoritN' of trees the fall takes 

 place acropefally. i.e.. the older leaves at the base of 

 the twigs fall first. 



It is well to notice that here again we have 

 order and not chance : that Nature has, as we 

 often find, two or more ways of bringing about 

 the same result ; and that even in such an 

 apparentlv simple matter as the fall of the leaf 

 there is room for a good deal more research. 



SOL.AR niSTl'RBANCES DURING NOVEMBER. 1910. 

 Bv FR.\NK C. DENNETT. 



DuRIXG November there ha.'; been a considerable falling ntl 

 in solar energy, a complete absence of dark spots being 

 recorded on sixteen days, and on five of these faculic 

 disturbances were also absent. It is a little peculiar that 

 the majority of the disturbances have occurred in the northern 

 zone, which for so long has been comparatively quiet. The 

 longitude of the Central Meridian at noon on Noxember the 

 1st was 18° 21'. 



As No. Si continued on the disc until November the ird it 

 is shown on the accompanying chart. 



No. 83. — .-X pore in the northern spot-zone, only seen on 

 the 3rd. 



No. 84. — Two pores only visible on the 7th, in the area 

 formerly covered by No. 75. 



No. 85. — A solitary pore also ephemeral, onlv being seen on 

 the 14th. 



No. 86. — First seen on the 16th, when it showed some of the 

 characteristics of an elliptical outbreak. The leader, or 

 western spot was 10,000 miles from north to south, and the 

 group about 3° in length. The spectroscope showed the 

 C line of hydrogen displaced both on the red and violet sides, 

 and prominences were visible in projection over the group. 



whilst the D:; line of helium was dark through the outbreak. 

 On the 17th it was seen as a nearly straight group of small 

 spots 40.000 miles in length. By the ISth it had assumed a 

 lozenge shaped arrangement of pores, with the largest behind, 

 or eastward, and when last seen on the 19th there were only 

 two pores, 26,000 miles apart. 



No. 86(7. — A single, not very bkick. pore a little west and 

 south of the group, only recorded on the 15th. 



No. 866. — A minute pair of pores 19.000 miles apart, in the 

 former area of No. 78, only seen on the ISth. 



No. 87. — Three pores nearly in line, also seen on the 18th 

 only, in the area of No. 79c. 



No. 88. — A single spotlet seen from the 20th until the 22nd 

 in a disturbed area, having apparently come round the limb. 



On November the 12th a cur\-ed faculic ridge of horseshoe 

 form was seen in northern latitude in the position dotted upon 

 the chart. 



The chart is constructed from the combined observations of 

 Messrs. J. McHarg, A. A. Buss, E. E. Peacock, and F. C. 

 Dennett, w^orking in places so far apart as Lisburn. Chorlton- 

 cum-Hardy, Bath, and Hackney, thus making the record 

 almost complete. 



DAY OF XOX'EMBER. 



