62 



PROPERTIES OP CELLULAR TISSUE. 



it may be inferred that this power is also possessed, by the simple 

 modification of it just described. Accordingly we find this to be 

 the case, fluids being conducted through cellular tissue very 

 readily from one part to another : but still it affords a sufficient 

 degree of resistance, to cause the transmission of fluids most 

 readily in the direction of the greatest length of the cells, where, 

 of course, there will be the fewest partitions in a given space. 

 Thus, therefore, fluids absorbed at the bottom of a stem, will pass 

 upwards through its cellular tissue more readily than in any 

 other direction, except in the case of the muriform cellular 

 tissue, which conducts fluids horizontally with the greatest readi- 

 ness. The object of these peculiar adaptations will be more fully 

 described in Chap, vi., where the structure and offices of the 

 different parts of the stem will be severally detailed. 



73. In the fabric of the lowest tribes of Plants, such as Sea- 

 weeds, Lichens, the Fungi (or Mushroom tribe), Liverworts, and 

 Mosses, little besides cellular tissue and its simple modifications 

 can be found ; and it forms a large proportion of the structure 

 of even the highest tribes. Thus in every Plant, the leaves, 

 flowers, bark, pith, and fruit, consist almost entirely of cellular 

 tissue ; and it is even found in the woody part of the stem and 

 roots, besides forming the largest proportion of those soft succu- 

 lent stems, which are only of short duration, dying as soon as 

 the fruit they bear has ripened. The whole of the young plant, 

 too, even of the highest tribes, consists, like the permanent forms 

 of the lower, of this kind of structure. It is only when the true 

 leaves have been unfolded, and are actively performing their 

 functions, that the other kinds of tissue show themselves. In all 

 newly-forming parts, also, the foundation, as it were, is laid with 

 this tissue, in which the others subsequently appear. So uni- 

 versally is it present, even in the adult fabric, that, if it were 

 possible to abstract all the others from it, the original form would 

 still be retained, except where it would give way with its own 

 weight. 



74. But, although cellular tissue is, in its regular state (of 

 which the pith of young twigs, or the pulp of fruits are charac- 

 teristic examples), soft and spongy in its character, it does not 



