CONTENTS. XVll 



CHAPTER XXIX. 



QUILLWORTS. 



Sporangia of isoetes, 398. Male prothallia, 401. Female pro- 

 thai lia, 402. Embryo, 403 page 196 



CHAPTER XXX. 



COMPARISON OF FERNS AND THEIR RELATIONS. 



Comparison of selaginella and isoetes with the ferns, 404. Gen- 

 eral classification of ferns, 407. Table showing relation of 

 gametophyte and sporophyte in the ptericjophyta,4o8. .page 199 



CHAPTER XXXI. 



GYMNOSPERMS. 



The white pine, 409. General aspect of the white pine, 409. 

 The long shoots of the pine 410. The dwarf shoots of the 

 pine, 411. Spore-bearing leaves of the pine, 412. Male 

 cones or male flowers, 413. Microspores of the pine, or 

 pollen grains, 414. Form of the mature female cone, 415. 

 Form of a scale of the female flower, 417. Ovules or macro- 

 sporangia of the pine, 418. Pollenation, 419. Female pro- 

 thallium of the pine, 422. Archegonia, 423. Male prothal- 

 lia, 424. Farther growth of the male prothallium, 425. 

 Fertilization, 426. Homology of the parts of the female 

 cone, 427 page 202 



CHAPTER XXXII. 



FARTHER STUDIES ON GYMNOSPERMS. 



Cycas, 428. Female prothallium of cycas, 429. Microspores or 

 pollen of cycas, 431. The gingko tree, 432. Spermatozoids 

 in some gymnosperms, 434. The sporophyte in the gymno- 

 sperms, 435. The gametophyte has become dependent on 

 the sporophyte, 436. Gymnosperms are naked seed plants, 

 437. Classification of gymnosperms, 438. Table showing 

 homologies of sporophyte and gametophyte in the pine, 

 439 page 214 



