ii2 



ABNORMALITIES OF THE LIFE-CYCLE 



[CH. 



laciniata, cristata, polydactyla, etc. by Moore(3oo), Lowe(3oi), Druery, and 

 others. Reference may also be made to Luerssen for a record of the con- 

 tinental examples (302). Such varieties bear, however, in so high a degree 

 the stamp of individual aberrations from the normal that they suggest that 

 they should properly be ranked as individual " sports." Nevertheless they 

 present many legitimate problems. From the comparative, rnorphological 



Fig. 305. A. Nephrodium Filix-})ias,miilti-cristata,\.o^&. A single pinna. (After 

 Lowe.) B. Nephrodmm Filix-inas, SchoJieldii,^\rA. Leaf twice forked. Reduced. 

 (After Lowe.) 



Fig. 306. Tips of pinnae from juvenile leaves o{ Nephrodium Filix-mas, 

 var. cristatum, raised apogamously in the Glasgow Botanic Garden, 

 1889. They show three progressive examples of cresting. A is 

 normal ; B the distal dichotomy is almost equally expanded ; in C 

 the right-hand shank is more profusely crested than the left. En- 

 larged. 



point of view the cresting is essentially a reversion. A leading feature in it 

 certainly is a partial, or indeed often a very perfect, return to that equal 

 forking which comparison shows to have been primitive (Chapter v). The 

 very gradual steps leading to this have been observed in crested pinnules 

 of Osmunda regalis. These give an opportunity of relating the forked 

 development to the regular dichopodial architecture of the normal leaf 



