DR. M. J. SCHLEIDEN ON PHYTOGENESIS. 295 



and in Leptosiphon androsaceum. Lastly, the lowest stage of de- 

 velopment is that where the gelatinous thread, which is furnished 

 with spiral striae, has a hollow cavity in its interior, which still 

 contains undecomposed starch ; this instructive appearance is 

 found in Dracocephalum Moldavica, Ocymum basilicum, and some 

 allied species. In illustration of the above, consult Plate XVI. 

 figs. 26-35, with their explanations. 



Before I quit the spiral fibre, I wiU merely add, what indeed 

 has been of late admitted by every good observer, that the only 

 difference between spiral cell and spiral vessel consists in the di- 

 mensions ; although constant transitions between them may be 

 observed quite as well as between the liber and parenchymatous 

 cells; and consequently, as regards the doctrine of this sub- 

 ject at least, there is no longer any place for natural philoso- 

 phical phantasies of rigid images of higher types, and such like 

 empty words. That which forms a cell of the Uber out of a round 

 cell, the preponderating expansion of an organ lengthwise, is also 

 that which converts the spiral cells (the vermicular body) into 

 spiral vessels. But the function of the spiral fibre is, as every 

 honest vegetable physiologist will certainly admit, entirely un- 

 kno^vn to us at the present day. It is certain that spiral vessels 

 and spiral cells occur in the living plant quite as frequently filled 

 with sap (in the young vegetating portions) as with air (in the 

 older organs which have attained their full dimensions) ; and it is 

 this which has given rise to the conflicting views of authors. 

 But the same also occurs in all cells under certain circum- 

 stances ; and the influence of spiral fibre remains totally in the 

 dark and unexplained. Perhaps it may seem probable from the 

 preceding that the spiral is everyn here only a secondary variation 

 in form in the product of the vital principle (the fibrous sub- 

 stance) produced by a different tendency of the vital activity 

 of the cell, as soon as this is forced, at a certain stage of its de- 

 velopment, to give up its independent individuahty, and to enter 

 as an integral portion into the complexity of the entire plant. 



Moreover I believe we may venture in conclusion to deduce 

 from the data above enumerated, that this indication of spiral 

 formation is the surest sign that we have no longer anything to 

 do with the simple cellular membrane. 



I now retvu-n, after this somewhat lengthy digression, to my 

 subject. The process of the formation of cells, which I have en- 

 deavoured to explain at full, is in effect that which I have ob- 



u 2 



