PHYSIOLOGICAL BOTANY. 231 



new parts occurs in the internodes themselves and not in 

 the nodes. He moreover says, "If we carefully examine 

 cellular tissue, in which new formations are in progress, 

 we find what is very remarkable, that all the cells are not 

 furnished with walls of equal thickness, but, on the con- 

 trary, that some of them are delicately constructed, whilst 

 others are scarcely perceptible. From this we may con- 

 clude that, in all probability, the latter are of a later for- 

 mation, and hardly entertain a doubt that any observer 

 will admit both the fact and the conclusion derived from 

 it." The next question was, whether the separating wall 

 was single or double. To determine this point, the 

 author selected some young hairs which were in the 

 earliest stage of development, from the recently-formed 

 leaves of Syringa vulgaris. He endeavoured, by the 

 action of chemical re-agents, to produce a condensation 

 and contraction of the finely granular contents, so as to 

 allow of the more perfect examination of the walls. 

 Dilute mineral acids answered tolerably, but the result 

 was best obtained by first subjecting them to the action 

 of caustic potash, and subsequently iodine. Even then 

 the separating walls always remain simple. Hence the 

 author thinks that this forms the commencement of a 

 subdivision into more cells, and therefore calls this form 

 of cell-growth merisinatic, but he is too hasty in his con- 

 clusions on this subject. As Unger expressed his dissent 

 from Schleiden's theory of cell-formation, the discoverer 

 of the spermatozoa (or whatever else they may be called) 

 in the anthers of the Mosses, and the ciliary motions of 

 the spores of the Algse, &c., receives the following repri- 

 mand in the 'Principles of Scientific Bot./ p. 210: 

 ' Transverse and longitudinal sections, and a mere glance 

 through a microscope, be this ever so good, are certainly 

 not sufficient now-a-days for making phytotomic inves- 

 tigations." 



In the first part of Schleiden and Nageli's ' Zeitschrift 

 fur wissenschaftliche Botanik' (Zurich, 1844), there is a 

 Memoir, by Nageli, upon the Nuclei of Cells, Cell-forma- 



