PHYTOGENESIS. 245 



Spiral faserzellen , &c., pp. 7, 8) is bused upon inaccurate ob- 

 servation. 



These cells are at first generally filled with starch; rarely 

 with mucus or gum. The starch always passes into the latter 

 substance in the progress of development ; and this 11 con- 

 verted into jelly, the change, as it would seem, taking place 

 from without inwards. This jelly finally is converted at its 

 outer surface into vegetable fibre, following the direction of a 

 spiral line, the coils of which are sometimes narrower, some- 

 times wider. When these forms are observed in their different 

 stages of development and in their various conditions, the idea 

 involuntarily forces itself upon the mind that the spiral forma- 

 tion is the result of a spiral movement of a fluid on the walls 

 of cells between them and the central jelly. Ilorkcl once 

 actually observed the motion of small globules between the 

 coils of the fibre in progress of formation in Hydrocharit. 



The great variety in the appearance of the fibres seems to 

 depend upon the period of their origin, and on modification in 

 the chemical changes of the formative material. It probably 

 depends solely upon the former circumstance whether the spiral 

 fibre lies free in the cell, when it is formed very late, or 

 whether it is blended with the membrane of the cell, if its 

 development commence at a period when the cell-membrane 

 itself is yet very soft and gelatinous, and may consequently 

 become agglutinated to the fibre, which is likewise still in a 

 gelatinous state. 1 This is the case in Casuarvna, Cassytha, 

 Hydrocharis, Trichocline, Orchis, &c. ; in most cases, however, 

 the cell-wall is too far developed to unite with the fibre, 

 and the latter then lies loose in the interior of the cell. In 

 rarer instances the material is almost entirely applied to the 

 formation of the fibre (always indeed when the fibre coalesces 

 with the wall), for example, in Salvia Spielmanni, M<>- 

 mordica elaterium. I have reason to suppose that this com- 

 plete consumption almost always takes place in spiral reatl Is, 

 and is the cause of their subsequently conveying only air. 

 More frequently, however, one or more fibres an 1 formed ; but 

 then a great portion of the jelly has still remained uncon- 



1 Subsequent researches, have produced important modification* in tbifl opinion. 

 Consult my essay on the Spiral Formations in Vegetable Cells. Ploi 18 ' Nea 



21, 22, PI. 



