40 ARUM. [CHAP. 



CHAPTER V. 



EXAMINATION OF COMMON PLANTS CONTINUED AS BEFORE. 



1. Arum. 



2. Spotted Orchis. 



3. Daffodil. 



4. Tulip. 



5. Wheat. 



6. Points of agreement in the four plants just examined. The 



structure and venation of their leaves, and the number of 

 parts in the flowers. 



7. A grain of Wheat is examined. Parts of the seed. 



8. Structure of the embryo of Wheat. There is but one coty- 



ledon. It is therefore monocotyledonous. Its mode of 

 germination. 



9. General characters of Monocotyledons. 



10. Scotch Fir. 



11. Tabular review of Angiosperms and Gymnosperms. 



12. These great Classes are divided into subordinate groups. 



13. The principal divisions of Dicotyledons, and the characters 



upon which they depend ; 



14. And of Monocotyledons. 



15. The Classes, Subclasses, and Divisions are tabulated. 



i. /COMMON ARUM or Cuckoo Pint. Without much 

 v^ care you will be liable to misunderstand the 

 structure of this plant, as did Linnaeus himself. The 

 flowers are closely packed in rings upon the lower part 

 of the fleshy spike, which you find enclosed in a large 

 sheathing bract-leaf called a spathe. A flower-spike of 

 this kind, enclosed in a spathe, is distinguished as a 

 spadix. With a magnify ing-glass compare the structure 

 of the minute flowers of the lower ring (p] with those of 

 the upper ring (st.\ Be careful to note, however, that 

 between the rings is a broken circle of abortive pistillate 

 flowers, and immediately above the upper ring a number 



