f 



222 



BOTANICAL GAZETTE 



[SEPTEMBER 



Polypodiaceae, suggested by Bower, there is a progress from coher- 

 ent to separate sporangia; from sporangia of definite orientation to 

 those indefinitely oriented; from imbedded to long slender-stalked 

 sporangia; from tapetum indefinite and derived from the tissue sur- 



FiG. 34. A section through the sporogenous mass showing some of the cells break- 

 ing down, X9S0. — Fig. 35. A sporangium near the apex of the pinnule; the spo- 

 rangium is beginning to break dowTi and will not produce spores. X980. — Fig. 36. 

 Another stage in the degeneration of a sporangium near the apex of a pinnule. X48o- 

 — Fig. 37. Still another stage in the degeneration of a sporangium near the apex of 

 a pinnule. X480. 



rounding the sporogenous mass to a definite tapetum cut off from the 

 central cell; from no annulus to annulus apical, oblique, and finally 

 vertical; and from indefinite massive sporogenous tissue, not all fertile, 

 but producing many spores, to a small definite sporogenous mass all 

 fertile and producing few spores. In all of these particulars Lygodium 

 falls short of the highest polypod type ; in all of them also it is above 

 the highest marattiaceous type. 



