DR. M. J. SCHLEIDEN ON PHYTOGENESIS. 291 



into connexion with my discovery, in order not to leave an appa- 

 rent contradiction unresolved. 



Meyen himself correctly observes, when treating of those spi- 

 ral tubes whose very naiTow fibres lie close upon one another, 

 that an enveloping membrane could indeed not be observed, but 

 thatthisby no means justified our concluding on its absence; for 

 if the thickenings of the cellular walls, which are formed in most, 

 perhaps in all cases, in spiral lines, in those places Mhere they 

 make their appearance early, even when the original cellular wall 

 itself is in statu nascentice and soft, are connected firmly with this 

 latter, and at the same time the simple coils of the spiral fibre lie 

 perfectly close on one another, so that with our present micro- 

 scopes no space between them remains perceptible, — it naturally 

 follows that on rupturing the entire membrane (the so-called 

 unrolling of the fibres) the rupture in the direction of the 

 coils of the fibre must be so sharply defined that our instru- 

 ments would not possibly be able to show the unevenesses. At 

 the same time it should be Avell remembered, that the original 

 cellular membrane, especially in long cells of hairs, frequently 

 mdergoes so great an expansion, that at last it would be infinitely, 

 ;hin, so that even the thinnest and apparently most simple 

 cellular wall would not exclude the possibility of its being com- 

 posed of the original membrane, and of the secondary deposit. 

 Vow if we set out from the spiral cells and vessels, the distant 

 :oils of which admit of no doubt as to the existence of an exte- 

 ior enveloping membrane, and if we follow up the presence of 

 his membrane through all the forms of the constantly approxi- 

 nating coils of the fibre until only the feebleness of our optical 

 neans prevents further dii-ect observation, the law of sound ana- 

 ogy would require us to admit even here the presence of a simi- 

 ar membrane. But there is yet a more direct mode of proof, 

 lamely the observation of the history of the develojoment. It 

 5 quite an essential law that each cell (laying aside for the pre- 

 jent the cambium) must occur in the form of a minute vesicle, 

 ;radually expanding to the size in which we find it in the deve- 

 )ped state. Moreover it is the constant result of an extensive 

 xamination of this formative process that a cell never evinces 

 trace of a spiral formation, either in its appearance or on 

 upture, previous to its complete growth, i. e. before it has reab- 

 orbed the cytoblast. In all spiral cells, cells which exhibit se- 



