THE VEGETABLE CELL. 9 



deceived if we deduced from the fibrous structure of these organs 

 a great length of the constituent cells ; yet, on the other hand, 

 cases do occur when particular cells exhibit an astonishing length. 

 The prosenchymatous cells of wood generally exhibit only a length 

 of l-3rd to one line, exceeding this last dimension but seldom; 

 as a rule, the bast cells attain abont the same length ; yet in some 

 cases they occm- of far more considerable length, for I found them 

 1*6 to 2*6 lines long in a Palm (a species of Astrocaryum). 

 The bast cells of flax and hemp are considerably longer, but difli- 

 cult to measure, since it is often impossible to ascertain the com- 

 mencement and termination of a cell Many hairs formed of 

 simple cells also exhibit a very considerable length, especially 

 cotton, the longest fibres of which do not, however, exceed one to 

 two inches. Among the cells of the higher plants the pollen grains 

 are the most striking for their great longitudinal growth, the fili- 

 form prolongation penetrating into the style attaining in long- 

 styled plants like IfiraSiKs longijiora, Oactus grandifiorus, <&c., a 

 lenefth of three inches and more. 



The most striking examples of large cells are found in the 

 family of the Algse, in many uni-cellular plants, as in Vaucherla, 

 Bryopsis, and especially in Ghara, in the larger species of which 

 the great cells forming the interior of the stem attain the length 

 of several inches, and a diameter of l-3rd of a line and more. 



C. THE CELL-MEMBRANE. 

 a. Physical Froperties. 



In most cases the membrane of cells possess a considerable de- 

 gree of stiffness and solidity. But in tliis respect extreme dif- 

 ferences occur between the cells of different plants and of their 

 different organs ; and, moreover, this condition may exhibit ex- 

 treme variations at different periods of the growth of the same 

 cell. The membrane of young cells, also the cells of many lower 

 plants, for example of most Algae, Fungi, Lichens, and the cells 

 of fleshy leaves and fruits are very soft ; while the cells of many 

 woods, e. g., in Palms and Tree Ferns, and those of the albumen 

 of many fruits, exhibit a bony hardness ; and finally, the cells of the 

 epidermis of Eq'wis&t'wm% and Calamus possess such solidity, that 

 it scratches metal, and strikes fire with steel. 



All membranes are readily penetrated by water, and in the 

 operation become more or less softened and swollen up. The latter 

 phenomenon occurs in a higher degree the younger and softer the 

 cell is ; whether, however, as ScHeiden states, the membranes of 

 nascent cells are actually soluble in water, is more than doubt- 

 ful to me. The swelling up occurs strongly in many thick-waUed 

 cells which in a dry condition have a horny consistence, as in 

 Lichens, Fucoidese, and in certain gelatinously soffc cells (the so- 

 called coUenchyma cells) lying beneath the epidermis of herbace- 

 ous plants. In the short parenchymatous cells no great difference 



