26 ELEMENTARY OEQANS OF PLANTS. 



spores. By a similar meohanism, the pollen is dispersed 

 from the anther-cells of Cohasa scandens. 



23. When the cell- walls of cellular tissue are composed of 

 membrane without fibre, it is called memhranous cellular tis- 

 sue ; but when the cell-waUs consist of membrane and fibre 

 combined, it is designated as _/?6ro-cellular tissue. Some 

 writers have recently distinguished other differences in the 

 figure assumed by the cells, by the employment of a variety 

 of technical terms expressive of those figures. But this is 

 only multiplying unnecessarily the technicalities of the 

 science. The general term, parenchyma, will suffice to dis- 

 tinguish a tissue composed of cells, from a fibrous tissue, or 

 that which is composed of fibres or tubular vessels. 



24. Cellular tissue enters largely into the composition of 

 all plants, forming the pith of trees, the pulp of fruits, and 

 filling up the interstices between the fibrous network of the 

 leaves. There is an extensive tribe of plants which are 

 wholly composed of this tissue, and as they produce no 

 flowers, they have been for these reasons called by botanists 

 ceUulares or flowerless plants. The orders comprised in this 

 division are the fungi, lichens, algae, liverworts, and mosses. 

 Of this tissue all plants in their earliest stage of development 

 are entirely composed. Indeed, plants, however complex 

 their organization, may all be traced by observation nearly 

 or quite to a single cell; which cell, endowed with the power 

 of self-propagation equally with the fully developed plant, 

 gives rise to other cells, each being individually possessed of 

 the same powers, and so forms the whole mass of the plant. 



