16 
ELEMENTS OF AGRICULTURE. 
QUESTIONS. 
1. What is the root ? 
2. Does the whole surface of the root contribute to the nourishment of 
the plant ? 
3. What is the spongiole ? 
4. What are parasitical plants 
5. What is the collar, or neck 1 
6. What is an annual root 1 
7. What is a pe^ ennial root ? 
8. How may an annual be sometimes made perennial ? 
9. How may roots be classed ? 
10. Why is it advisable to cultivate roots 1 
LESSON V. 
THE STEM AND LEAVES—FUNCTIONS THAT THEY FULFIL 
IN THE ACT OF NUTRITION. 
27. That part of the plant which, starting from the col¬ 
lar, springs erect above the surface of the ground, in search 
of light and air, is called the stem. 
28. Stems are divided into several kinds, depending up¬ 
on form and substance. Those resembling the stems of 
trees, bear the name of trunks ; and those that are hollow 
and jointed, are called stubble, as the stems of wheat, and 
other cereal plants. There are plants without any stems. 
29. When a stem has the consistency of wood, it is 
called ligneous ; when it is tender, like grass, it is called 
herbaceous . 
30. The parts composing the stems are much more dif¬ 
ficult to distinguish in some plants than in others. Thus, 
in herbaceous plants, they are not easily detected ; whereas 
in trees, we may almost always distinguish the different 
parts composing the stem. 
31. The trunk, or stem, is divided into the following 
parts: 1. A dry, leathery, tough membrane, the cuticle . 
2. A cellular layer, adhering to the cuticle, and called the 
