LIFE OF THE PLANT-CELL. 91 



Individual cells are frequently entirely filled with essential oil or with 

 resin, or with a substance not yet chemically determined, of a red or 

 brownish colour, which is found in the cells of many Algce (the hologo- 

 nimic cells of Kutzing). In the green cells in a state of active vegetation, 

 the following appearances are usually observed : the internal surface is 

 invested with a continuous and very delicate layer of semifluid mucus 

 (" amylid-cell" of Kutzing, " primordial utricle" of Mohl), to which the 

 more solid mucus and starch granules adhere ; these granules are usually 

 covered by chlorophyll in a semifluid state, or that substance is attached 

 to the mucous layer, occasionally, as in the species of Spirogyrce, in 

 spiral bands jagged at the edges.* The chlorophyll may be merely 

 deposited upon the starch, or it may be, perhaps, that starch is formed 

 into chlorophyll, but never from it. Chemistry is wholly opposed to 

 the latter being the case ( 12. 1.). The rest of the space in the cell is 

 usually filled with a thin, tolerably clear fluid a mixture of dextrin, 

 sugar, and albumen in solution, in the most varying proportions ; and not 

 unfrequently also containing more minute, semifluid, mucus-granules, 

 inulin, extremely minute oil-globules, and chlorophyll, distributed in 

 various ways : inorganic crystals, on the other hand, are rarely met with 

 in cells in a full state of vitality (as is sometimes the case in Spirogyra). 

 Of these matters, however, one or the other is occasionally wanting, or 

 exists in greater or less proportion. Crystals, especially when in great 

 numbers, usually occur only in an aqueous fluid containing few organic 

 compounds, as, for instance, dextrin : oil and resin are frequently found 

 alone. As to the forms exhibited by these substances, all that is 

 necessary has been already said ( 7. 9, 10.) : I will here merely notice, 

 in addition, two very remarkable conditions. 



a. Upon examining the fibres of the root of Neottia Nidus avis (in 

 flower), three layers of cells will usually be observed immediately 

 beneath the epidermis ; the first consisting of cells about three times as 

 long as the epidermis cells, and of the same breadth ; the second and 

 third, of cells of the same length as the former, but as broad as long. 

 Immediately on the inside of these succeed cells of the same breadth, but 

 three or four times longer, containing starch. Each cell of the outermost 

 of these three layers contains an elongated irregular mass of a semi-solid 

 yellowish substance (coagulated mucus?), which occupies nearly the 

 whole of the cell. Each cell of the internal layer is filled in the same 

 way, but in them the contents are intermixed with distinct fibres. The 

 cells of the intermediate layer, lastly, contain a globular mass of a 

 material of a browner colour which almost fills them ; this globular mass 

 is not composed of an amorphous substance, but, on the contrary, is con- 

 stituted almost entirely of interlaced fibres, very similar to those which 

 occur in the internal layer of cells. These fibres, which at first sight 

 might be taken for spiral fibres, are seen, on stricter examination, to be, 

 in the first place, all confusedly entangled, and, secondly, to be not solid 

 but to constitute tubes with unyielding walls and of moderately wide 

 calibre. They frequently present irregular dilatations and short lateral 

 coecal branches, and they not unfrequently subdivide into longitudinal 

 branches. They also exhibit dissepiments at regular distances, especially 

 towards their extremities, which are rather dilated ; these dissepiments 



* Kiitzing's notion that the amylid-cell is contracted into these spiral bands (Phy- 

 cologia generalis, p. 49.) is to he attributed to the want of precise observation. The 

 soft mucus investment co-exists in a perfect state together with the spiral bands. 



