42 ELEMENTS OF PLANT ANATOMY. 
permanency of such combinations, they may be regarded either 
as individuals or as colonies of single cells. If we consider the 
colony as representing the lowest type of plant tissues, the next 
higher is that found most frequently among fungous growths ; 
this is generally called false tissue, as its mode of origin and 
development differs in certain respects from that composing 
ordinary plants. False tissue may be described as arising from 
a combination of branches either of a single cell, or of a number 
of cells, interwoven in sucha way that their walls grow together, 
forming a compact body. Subsequent growth may occur and 
the number of cells may increase by new walls forming at right 
angles with the long diameter of the branches. The number of 
cells may also be increased by new branches growing and forcing 
their way between the old, separating the double walls at 
the place of their previous union. This kind of growth is found 
in all the higher classes of fungi, large and strong masses of 
tissue arising in this way. Several kinds of algae grow partly 
in this manner. 
The term true tissue is applied to that constituting the bulk 
of ordinary plants. It arises from cell division, the new walls 
extending, in most instances, in all three directions, and at 
various angles with the old. Formerly it was believed that one 
principal characteristic of false tissue was the separation of cells 
once grown together, by means of new branches crowding their 
way between. ‘There is now considerable evidence that parts 
of true tissue develop in a similar manner by a process called 
gliding growth, a common wall between two cells being split 
apart by the ingrowing of an adjacent one. If this is true, 
there is not so much difference in the manner of development 
of the two kinds of tissues. The lower grade is still marked by 
the new walls always forming at right angles to the long axis 
of growth. 
Taking up now the consideration of tissues in the restricted 
sense of the term, it is difficult to estimate the exact number 
