294 DR. M. J. SCHLEIDEN ON PHYTOGENESIS. 



surface into vegetable fibre, following the direction of a spiral 

 line, the coils of which are sometimes narrower, sometimes 

 wider. If these forms be observed in their successive stages 

 of development and in their various conditions, the idea in- 

 voluntarily forces itself upon one that the spiral formation arises 

 from a spiral movement of a fluid on the walls of the cells be- 

 tween them and the central gelatin. Horkel has once actually 

 observed, in Hydrocharis, the motion of small globules between 

 the coils of the fibre whilst in the act of forming. 



The highly varied appearance of the fibres seems to depend 

 chiefly upon the time of their origin, and on modifications in the 

 chemical changes of the formative substance. It probably depends 

 solely upon the first circumstance, whether the spiral fibre lies 

 free in the cell when it is formed very late, or whether it is ad- 

 hering to the membrane of the cell, if its origin happens at a 

 period when the cellular membrane itself is still very soft and 

 gelatinous, and consequently can glue itself to the fibre, likewise 

 still in a gelatinous state. This is the case in Camarina, Cassy- 

 tha, Hydrocharis, Trichocline, Orchis, &c., but in general the 

 wall of the cell is too far advanced to unite with the fibre, and it 

 then lies loose in the interior of the cell. In this case the ma- 

 terial is rarely consumed entirely in the formation of the fibre 

 (although it always is Avhen the fibre coheres with the wall) e. g. 

 in Salvia Spielmanni, Mormordica elaterium. I have reason to 

 suppose that this complete consumption almost always takes 

 place, especially in spiral vessels, and is the cause of their 

 conveying only air. More frequently, however, one or more 

 fibres are formed ; but then a great portion of the gelatine has 

 still remained unconsumed, which, on moistening the cell with 

 water, oozes out in a vermicular form, and in swelUng expands 

 itself over the fibres, thus appearing to surround them ; this is 

 the case in most Salvia and Polemoniaceae, in Senecio flaccidus, 

 Ocymum polystachyum and polycladum [Lumnitzera, Jacq.). 

 There is an intermediate form between this and the former Avhen 

 the gelatine itself forms a broad spirally wound band, which ap- 

 pears to be composed at its surface of innumerable delicate fibres ; 

 their occurrence in this state is very beautifully seen in Perdi- 

 cium Taraxaci and Ziziphora, A much less advanced formation 

 exhibits merely a thread or a cone of gelatine in the interior of the 

 cell, the surface of w'hich, however, is covered with delicate spiral 

 lines. This occurs in some Salvia, for instance in S. verticillata, 



