12 THE AMERICAN BOTANIST. 



linated. The change, however, is doubtless due to a differ- 

 ence in the cell sap at different ages in the i^ower and would 

 probably occur whether the flower was pollinated or not. If 

 the insect is a gainer in the matter it is simply his good for- 

 tune. 



Ferns and Drouth. — It is well known to botanists that 

 drouth is very effectual in causing plants to flower and fruit, 

 and the same thing seems applicable to the fern-worts. 

 The behavior of the various species of Marsilia are quite in ac- 

 cordance with the rule. \A'hen growing in plenty of water 

 they rarely fruit at all. Fruitino- specimens must be looked 

 for among the dilapidated specimens in drier ground. The 

 same is true of Pilularia and the species of Isocfcs. Some of 

 the so-called "terrestial" species of the latter fruit at the begin- 

 ning of the dry season, and then drop their leaves, but if sup- 

 plied with water throughout the year do not drop their leaves 

 and rarely produce spores. Other species fruit late in summer 

 when most likely to be exposed to drouth. The fact thus illus- 

 trated is of wide application among the ferns, and may have 

 an influence upon the production of such forms as Onoclea 

 sensibUis obtusilobata and Osiiiinida cinnainomca frondosa. 

 Many have conjectured that the last mentioned form is due 

 to a fire sweeping through the locality, while others claim to 

 liave found specimens where there were no signs of a forest 

 fire. Drouth at the proper season. howe\'er. might account for 

 both occurrences. Prof. Atkinson has held that the obtusilo- 

 bata forms of Onodca and Stnitliioptcris can be produced at 

 will by removing the early sterile fronds, but- some of those 

 who have tried to duplicate his results have been unable to 

 do so. It may turn out, after all. that dry weather must be 

 taken into account in producing such forms. Many other hab- 

 its of ferns point to this theory. Practically all tropical ferns 

 fruit at the beginning of the dry season, and our own ferns, 

 with few exceptions, fruit when their habitat is the driest. 



