129 



On the Histology of Plants. 



By E. Braithwaite, M.D., F.L.S. 



1. Structure and Contents of the Plant Cell. 



{Read Januarij 24, 1873.) 



In tlie subject I now bring to your notice, I bave no original 

 investigations to offer; my aim bas simply been to pLace before you 

 tbe more important facts so ably treated on by Von Mobl, Prings- 

 li€im, Sachs, and Dippel, trusting that, in a field so rich, some of 

 our members may become workers, or at least recij^ients of some- 

 thing novel or instructive. 



Linnaeus despised the microscope, and all information it supplied, 

 and hence was far behind his predecessor Malpighi in a true know- 

 ledge of vegetable structure, but Mirbel, Amici, Schleiden, Von 

 Mohl, Hoffmeister and others, have in our own limes taken up the 

 thread dropped at the end of the seventeenth century, and laid 

 before us in all its minuteness and perfection the wonderful fabric 

 of plant organization. 



If we set before us a part of one of the higher plants, a branch 

 or a leaf of this Magnolia, for instance, we require but little mag- 

 nifying power to observe that it is built up of very different ele- 

 ments — of pith, and wood, and bark, in the former, and of a central 

 fibro-vascular skeleton and pulpy pareuchyma, protected by a hard 

 cuticle or skin in the latter. Yet, if we trace back the growth of 

 such a tree to its parent seed, and examine the embryo of that seed 

 from which the wLole has been developed, we find no such distinc- 

 tions, but only uniform cells ; and if we turn to the animal king- 

 dom, the case is the same, for from the cellular germinal vesicle of 

 the ovum is developed by its inherent life forces, the bone and 

 muscle, tbe blood and brain, that constitute the living entity of each 

 one of us now present. Again, as we descend the scale equally of 

 animal and vegetable existences, we find less differentiation ofpaits, 

 until we arrive at those lowest members of each, wbere, within the 



JouRN. Q. M. C. No. 22. k 



