DEVELOPMENT AND FUNCTIONS OP CELLS. 39 



is a similar development of buds or new plants on the stem, 

 but not to the same extent ; hence they do not attain the 

 same elevation above the ground. In the lower forms of 

 herbaceous vegetation, the buds or stem-plants become suc- 

 cessively less and less evolved, until at length they disappear 

 altogether from the stem, which itself is so contracted in its 

 growth as to be hidden in the earth. This is the case with 

 the hyacinth, lily, and other bulbous-rooted plants. The 

 bulbs of these plants are considered by botanists to be subter- 

 ranean buds or undeveloped stems, to which they are in every 

 respect similar. The outer leaves of these buds retain their 

 rudimentary soalelike appearance, and form a protective 

 covering to the inner leaves, which grow in a tuft on the 

 ground, the flower-stem rising from their centre. 



42. In all these instances, the parts consist of millions of 

 vegetative and reproductive cells, especially when the plants 

 attain any considerable degree of elevation above the earth's 

 surface, as in the case of forest-trees, where the evolution of 

 cells goes on for centuries. In the lower forms of vegetation, 

 the vegetative and reproductive cells become successively less 

 and less evolved, until at length, by successive degrees of 

 simplification of structure, all distinction into organic parts 

 gradually and finally vanishes. 



43. In the beautiful and interesting tribe of plants called 

 Ferns, we have a still greater simplification of vegetable struc- 

 ture. Stem and leaf are now blended into what is designated 

 a frond, which appears to partake of the nature and office of 

 both, whilst in place of the beautiful flower there is only a 



