COMPARED WITH THOSE OF ANIMALS. 



33 



vasiform tissue and spiral vessels, the last being particularly 

 abundant in the neighborhood of the pith. 



Fig. 3. 



Longitudinal section of Italian reed, a, Cells of the pith ; b, annular ducts ; 

 e, spiral duct ; d, dotted duct ; e, woody fibre ; /, cells of the herbaceous integu- 

 ment, one of the epidermal layers. 



It is not difficult to follow this transformation through its 

 successive stages, and thus to arrive satisfactorily at the im- 

 portant physiological fact of the individuality of the cells. 

 It is only necessary first to examine the stem or any other 

 organ in the embryonic condition, and then at intervals, 

 soon after active life has begun to manifest itself in the 

 germ. 



If we observe the fibrous portion of the wood, for instance, 

 when germination commences, we shall see that at first the 

 fibre cells consist of a row of utricles somewhat more 

 elongated than the neighboring cells ; gradually these 



