258 PHYSIOLOGICAL BOTANY. 



shows, that the lower internodes first cease to grow. 

 Investigations upon the growth of the shoot of Tilia 

 parviflora follow, arranged in tables ; these include : in- 

 crease of the individual internodes in length ; increase of 

 an individual internode at different ages ; increase of the 

 pith ; multiplication of the cells of the pith ; increase of 

 the longitudinal and transverse diameter; of vascular 

 and liber layers ; transverse diameter in proportion to 

 the longitudinal; parenchymatous layer of the bark; 

 number of rows of cells, proportion of the diameter of 

 this layer to the diameter of the internode, increase of 

 the cells of this layer in comparison with the increase of 

 the cells of the pith ; Schleiden's callenchymatous layer,* 

 i. e. the layer of remarkably long cells, which exists 

 beneath the epidermis in many plants ; number of cells 

 in the peripheral layers. We next have similar investiga- 

 tions upon Humulus Lupulus, as also upon the nucleus 

 (cytoblast) in the cells of the pith, the corpuscles existing 

 in the layers of the liber, and the growth of a shoot, 

 which had been deprived of its leaves at the apex. Again, 

 investigations upon the shoots of Aristolochia Sipho, Phy- 

 tolacca decandra, and Sempervirum arborescens. Then 

 follow the results : 1. The growth of each internode de- 

 pends upon the formation of new cells, the expansion of 

 the cells, and the thickening of their walls. 2. The multi- 

 plication of the cells takes place in three directions : in that 

 of the radius radial growth ; in that of the periphery 

 peripheral growth ; and in that of the axis longitudinal 

 growth. 3. The radial multiplication only occurs in the 

 buds. 4. This multiplication is produced by means of cross 

 septa, which are formed in the previously existing cells, 

 without the latter becoming subsequently absorbed ; the 

 subdivisions thus formed continually become more and 

 more isolated, in consequence of their expanding on all 

 sides. 5. The expansion of the cells in the radial direc- 

 tion is uniform and equal, so that the diameter always 



* " A term as elegant as it is superfluous," as Schleiden once said against 

 me on a similar occasion. 



