Chap. II] PERIODIC PHENOMENA IX TEMPERATE ZONES 4-^-, 



is however occasionally converted into starch (transitory starch). The 

 path of this stream of glucose is always the same. It is determined in 

 the leaves by the elongated parench)-ma-cells of the nerves and petiole, 

 and in the axes is confined to the cortical parenchj'ma. From the cortex 

 the stream flows horizontally into the wood, where the parenchyma-cells 

 gradually fill with starch, whilst the vessels retain as such the gluco.se 

 they have received from the parenchyma. There is no descending cuncnt 

 of assimilated matter in the wood. 



The coimnciiconcitt oj leaf-fall indicates in the tree the vwnicnt at zvhich 

 the tree contains the greatest amount of assimilated matter (autumnal maxi- 

 muin). E'rom now onw ards up to the beginning of the~next^egctatrve 

 season a continual diminution in that amount takes place, at first slowly, 

 but finally very rapidly. 



Immediately after reaching its autumnal maximum, which is al.so 

 specially that of starch (autumnal starch-maximum), the assimilated matter 

 within the axes is distributed in the following manner : — The parenchyma of 

 the cortex and of the medullary ra}s is rich in starch and glucose ; the 

 cambium contains neither. The_a:oo d contains much starch but no glu cose 

 in its^ living cclls ^much glucose but no starch in the vessels._ The medul- 

 lary sheath is rich in both substances ; on the other hand the\- occur in 

 the pith here and there only. 



Shortly after leaf-fall the starch completely disappears from the cortex, 

 as it is co nverted p a rtly into g lucose and some fat, pa rtlyjnto. somp still 

 unknouin_j3odjes_(sj2ecjes of sugarV The w ood is somewhat poorer ^rt 

 glucose than during summer, b uLshows-no^percept ible diminution in the 

 quantity of starrh if ronfains. 



The buds at the time of the starch-maximum contain no glucose, but 

 the scales are rich in starch, and the pith still more so. The embryonic 

 organs are devoid of starch and glucose. 



Towards the end of winter, even before any externally visible changes 

 indicate the commencement of the vegetative season, activity commences in 

 the interior of the tree. The cortex free from starch becomes again filled 

 with this substance, clearly at the cost of the glucose and of the unknown 

 bodies formed during autumn (spring starch-maximum). This condition 

 is onl\- of short duration. The starch is again partly converted into 

 glucose and this flows into the vessels. In the vessels the current of sap 

 sets itself in motion and provides the buds — hitherto poorly supplied with 

 water and nutriment — with water and glucose. 



Even in the buds, mo\-ements in the reserve-material have taken place 

 during the winter-sleep. The starch has left the pith, where it was at 

 first so abundant, and has now accumulated in the embryonic leaves and 

 flowers, from which hitherto it had been absent. It is reserve- materia I, and 

 just suffices for the first stages in the flushing of the buds, that is, up to 



F f 2 



