30 FAMILIAR LESSONS IN BOTANY. 



of assimilation. You see, therefore, that leaves perform 

 the threefold function of mouth, lungs, and stomach. 



68. What I told you concerning the root is equally appli- 

 cable to the leaf; great care is to be observed concerning 

 its shape, etc. Often a species is determined entirely by 

 the leaf. Thus the violet family is divided into several 

 species, the difference in the leaf constituting their basis, 

 as the violet sagittata, violet roticndifoUa, that is, arrow- 

 shaped and round leaves. 



69. When plants are destitute of leaves, which is some- 

 times the case, they are said to be apliyllous. Mushrooms, 

 some seaweeds, garlic, rushes, etc., are all aphyllous, with- 

 out leaves. 



70. The first leaves that appear are seminal, from semina, 

 seed, and are named cotyladons, or seed lobes. Those that 

 appear first after the seed leaves are called primordial. 

 Those upon the fully matured plant are styled character- 

 istic. When the leaf springs from the root, like the dock 

 and plantain, it is said to be radical ; when from the 

 stem, cauline ; when on the stem, sessile. And we de- 

 scribe their position further by the terms alternate and 

 opposite, as they may be situated, thus : 



Fig. 15.— Opposite. Fig. 1G.— Alternate. 



71. The duration of all leaves is not the same. Some 

 fall off as soon as they expand, and are then said to be 



68. Why must care be observed relative to the form of the leaf ? 



69. When a plant is destitute of leaves, what is it called ? 



70. What are the first leaves called ? Have they any other name ? What is 

 seminal derived from ? Those that succeed them ? Those on the mature plant ? 

 When a leaf springs from the root ? When from the stem ? How are they farther 

 described ? 



71. Is the duration of the leaves the same? If they fall off as soon as they 

 expand, what arc they ? What arc deciduous leaves ? What persistent ? 



