Substances in the Stems of certain Deciduous Trees. 73 



Material of the Liriodendron collected on Oct. 20, 1897, 

 was upon examination found to have an abundance of starch in 

 the cells of the cortex but none in the cells of the medullary 

 sheath and but few grains in the cells of the wood parenchyma 

 and medullary rays. The cells immediately below the grow- 

 ing point of the stem contained no starch at this time. At 

 this time practically all the leaves had fallen and the amount 

 of starch now present represents the maximum amount. An 

 examination of twigs from the same tree during the months of 

 November and December showed a gradual increase in the 

 amount of the starch in the medullary sheath but a marked 

 decrease in the amount present in the cortex. During all this 

 time there was some starch in the wood parenchyma and even 

 more in the medullary rays. There was at this time a con- 

 siderable amount of starch in the pitted cells that form plates 

 across the pith in this species ; but none was found in the 

 other cells of the pith, which latter had no protoplasmic con- 

 tents. The cells below the growing point up to this time con- 

 tain no starch and in fact none is found there till about the 

 first of March. The January collections show a gradual reduc- 

 tion of the amount of starch in the cells of the wood paren- 

 chyma and the medullary rays and medullary sheath. We 

 reach finally a period at the end of February when starch begins 

 to appear again in the cortex but more especially in the cells 

 which lie beneath the growing point, i. e. in that dome-shaped 

 group of cells that is called the pith cap. The cells of this 

 cap are much the same in histological structure as those of the 

 medullary sheath. The last collections, those of March, show 

 still more starch in this region above the pith cap and less in 

 the medullary sheath with quite a large quantity in the cortex. 



The same statements will hold good for Pyrus malus except 

 that some starch was found in the medullary sheath, medullary 

 rays and the wood parenchyma on Oct. 20, 1897. In this 

 species some starch could be found in the cortex all winter but 

 in other respects the starch distribution was much the same as 

 in Liriodendron. 



The facts just stated for these two species will hold good, 

 with slight individual variations, for the other species exam- 

 ined. In trees growing under our conditions I have found no 

 such marked reduction in the total amount of the starch in the 

 twigs as was reported by Fischer, '8S and '90. The only altera- 

 tions I find are simply a general movement of the starch from 

 the more peripheral and exposed regions to the more deep- 

 seated and protected regions of the stem during the winter 

 and a return again in the spring to the cortex and the regions 

 of growth. 



Further studies, now in hand, will trace the condition of the 



