90 PHYSIOLOGICAL PROCESSES IN PLANTS 



Conclusions. 1. What seems to be the purpose of the sticky material 

 on the bud scales of horse-chestnut ? 



2. What do you think the old ring of scars represents ? The new ring 

 of scars ? 



3. Of what use is the overlapping of bud scales ? 



Observations. 1. What is the appearance of the inner part of the bud ? 

 2. Where are the inner parts of the bud attached ? 

 Conclusions. 1. What structures are contained in the bud ? 



2. What is gained by having these structures well developed in the 

 bud? 



3. How do the structures stowed away in the horse-chestnut bud 

 compare with those in the lilac ? What is the object of the rolling or fold- 

 ing? 



4. Why are the buds that live but one year unprotected ? 



5. Would tropical trees be as likely to have buds protected as those in 

 colder regions ? Explain. 



6. Why do most of our common plants have buds ? 



7. What would happen if a plant had no buds ? Explain. 

 Observations. 1. Examine the opening buds of the winter twigs pre- 

 viously placed in water. What do you find ? 



2. Find fresh scars. What do they represent ? 



3. Cut a Brussels sprout or a cabbage head lengthwise through the mid- 

 dle. Explain what you see. Are there any protecting scales ? Is there 

 astern? 



Conclusions. 1. What structures are contained in the bud ? 



2. Why are buds of plants that produce seeds the first year and then 

 die, unprotected ? 



3. Name some buds useful as food. 



PROBLEM XVII 



The structure and work of stems. 

 Note. A stem is a developed bud. 



a. External Structure of a Dicotyledon (Optional) 



Materials. Stems of horse-chestnut, lilac, etc. 



Observation. Find leaf scars or traces above the buds, along the 

 sides of the stem. What do they represent ? Do you find small scars 

 here arranged somewhat horseshoe-shaped? If so, they are the broken 

 ends of the hollow tubes (fibro vascular bundles) mentioned under the 

 study of root hairs. We found them to originate in the root hairs, from 



