176 BIOLOGICAL LECTURES. 



Stool where were three freshly developed sterile leaves. The 

 sterile leaves were 60-75 cm. in height, and the transformed 

 sporophyll about 30 cm. The leaf was somewhat injured by 

 accident, perhaps by the knife when cutting the sterile leaves 

 on the 14th. The pinnas were fully expanded, yet markedly 

 different from those of the sterile leaves, being only toothed, 

 while the pinnae of the sterile leaves are deeply cut and possess 

 quite acute pinnules. The teeth, or pinnules, of the trans- 

 formed fertile leaf were obtuse or rounded. This was the only 

 marked difference at first observed, and I did not feel warranted 

 in concluding that it was a fertile leaf until examination with a 

 pocket lens revealed plainly a number of rudimentary indusia. 

 There were no sporangia, however, not even rudimentary ones, 

 and none of the pinnules were at all revolute. 



The experiment with Onoclea struthioptens being somewhat 

 unsatisfactory, because undertaken so late in the season, was 

 renewed this year (1895). The first vegetative leaves were cut 

 early in May, when they were about 40 or 50 cm. long. This 

 species differs markedly from Onoclea sensibilis in the vernation 

 of the leaves. Those of Onoclea sensibilis are developed suc- 

 cessively one by one on a prostrate rhizome, or stem, which 

 advances so rapidly that the leaves of one season stand in a 

 row. In Onoclea struthiopteris the stem is perpendicular and 

 increases in length very slowly, the leaves being developed in 

 rosettes, a half dozen, more or less, at one time. 



The experiment plat was visited a second time early in June, 

 and a second rosette of leaves had developed from the stools 

 which had been cut in May. This time the leaves were about 

 30 cm. high. None of the sporophylls had appeared, and the 

 leaves were cut again. Leaves from undisturbed plants were 

 also cut at this date. Late in June a few of the sporophylls 

 were appearing from a very few of the untreated plants, but 

 none as yet showed from the amputated plants, though another 

 large rosette of vegetative leaves had developed. The season 

 was a very dry one, and very few sporophylls had developed, 

 and for this reason the experiment was considered a failure. 

 However, July 29th a sudden impulse seized me to visit the ex- 

 periment plat again, and this time not in vain, for eight to ten 



