17. How are the seeds spread?
18. What climate is needed for rubber trees?
19. Which country formerly supplied all the rubber used in the world?
20. Who first thought of growing rubber trees on plantations?
21. Why did he think it was better to grow them on plantations?
22. How were the rubber seeds taken from Brazil?
23. On what tropical island was the first plantation started?
24. Where are rubber plantations found to-day?
25. What is the yearly output of the plantations?
26. What was the curious coincidence in the growth of the plantation industry?