44 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 



ning meristems have had a regular and orderly phylogenetic history {cf. 

 Bower, 1889). From the meristem a more or less homogeneous paren- 

 chyma is directly derived. Very soon, however, farther differentiation 

 occurs in the older parenchyma the parts farthest removed from apical 

 meristem. This differentiation has also been modified in course of time 

 in response to the environment and the needs of the plant. But there is 

 no reason to suppose that the changes in the meristem should have any 

 direct relation to those in the older portions. Meristem develops from a 

 growing point and its structure is influenced largely by the shape, size, 

 number, and position of the initial cells. Mature tissues develop from 

 below upward, and are shaped out of meristem in response to stimuli 

 which come chiefly from the more mature cells. While this independence 

 of meristem and mature tissues seems plainly indicated by a comparison 

 of plants as they commonly occur, it is also capable of experimental inves- 

 tigation. Some of the most promising material for this purpose would be 

 in the genera Gleichenia {cf. Boodle, 1901) and Lindsay a {cf. Tansley and 

 Lulham, 1902). But this is a subject which has yet to be followed out. 



Synony7ny of generic names , and list of type species on strict Linncean priority. 



1. Polypodium Linnaeus, 1753 Type: P. lanceolatum (first species named.) 



2. Dicksonia L'Heritier, 1788 Type: D. culcita (or D arbor escens}. 



3. Aspidium Swartz, 1800 Type: A. articulatum (fide Underwood, 1899). 



4. Dennstcedtia Bernhardi, 1800 Type: D.flaccida=Trichomenesflaccidum Forst. 



5. Nephrodium Michaux Date and type uncertain. Cf. Underwood, 1899, p. 265.* 



6. Sitobolium Desvaux, 1827 Type: S. punctilobum. 



7. Sitolobinm J. Smith, 1841 Type: S. punctilobum. 



8. Litolobium G. Kunze, 1848 Type: L. punctilobum. 



9. Adectum Link, 1841 Type: A.pilosiusculum. 



*Cf. Davenport in Rhodora, 4:is8 ff., Aug. 1902. 



