1909] 



LEAVITT—HOMOEOSIS IN PLANTS 



33 



grow 



poor conditions, they generally revert temporarily, in a part of their 

 fronds at least, into the primitive state, which is seen to be that of 

 the Boston fern. This constitutes highly desirable proof of parentage. 



Whether the sudden alteration of character took nlace in a snore, or 



from 



Nevertheless 



cumstances leave little doubt on this head; for the Boston fern, while 

 richly stoloniferous, is almost universally sterile. Mr. Pierson 



believes the original individual to have been 



port. The 



young plant caught the eye of a gardener, who brought it to the 

 notice of Mr. Pierson, and it was set aside so that its development 

 might be followed. All Pierson 



ferns 



from 



may 



the leaves of the fern and consists not in the introduction of alto- 

 gether novel outlines or 

 proportions, but rather in 

 the relocation of forms 

 already in existence, has 

 taken place under observa- 

 tion. A single individual 

 has been noted to emerge 

 from the common mass — 



as an 



very 



under cultivation 



isolated colony— with 



markedly altered characters. 



New features have not been slowly 



generations, but have appeared suddenly. 



Fig. i. — Pinna of Boston fern. 



developed through several 



The Boston fern has. 

 serrulate-margined 



sim 



fronds. The pinnae are 

 and usually bluntly toothed or 



margin at base (fig 



In the new plant, 



ted 



developed, toothed or auriculate on the upper margin 



often much elongated. Their divisions, the pinnules, are oblong and, 

 *-hen fully " r 



\fig- *). ine pinnules, in fact, are very goo< 



each 3 ^ Cn the nCW f ° rm is ful, y ex P r essed. The division may 



