Regeneration 233 



another by plasmolysis, and each then grows into a new plant. Among 

 simpler fungi almost any adult cell on isolation will give rise to a new 

 mycelium. Kerl (1937) found that single cells from the surface of 

 Pi/ronema confluens would do this. Such instances could be multiplied 

 almost indefinitely. 



Individual cells, if injured, will often restore themselves, especially large 

 ones like those of Vaucheria ( Weissenbock, 1939 ) , Dasijcladus ( Figdor, 

 1910), and Acetabutoria (Hammerling, 1936) or the coenocytes of Bryop- 

 sis and Caulerpa ( Janse, 1910; Winkler, 1900; Dostal, 1926). In such algae 

 as S-phacelaria, which grow by an apical cell, this cell may be replaced, 

 if injured, by the cell next below it, which first undergoes considerable 

 reorganization (Zimmermann, 1923). Other cases have been described. 

 Hofler (1934) observed in the filamentous alga Griffithsia that, if a cell 

 dies, the one above it will send a tube either through it or around it 

 which makes connection with the cell below and thus restores the con- 

 tinuity of the living filament. 



In the early development of certain animal embryos, if one of the first 

 two blastomeres is killed, the other develops into an entire organism. A 

 somewhat similar instance in plants occurs in Fucus. Here, after the fer- 

 tilized egg has formed two cells, an apical and a basal (rhizoidal) one, 

 the apical cell will produce a new rhizoid at the basal pole if the first is 

 destroyed (Kniep, 1907). Setchell (1905) in his studies of the kelps de- 

 scribes the way in which a stipe, if the blade is cut off from its tip, will 

 regenerate a new one from the cut surface. This commonly happens in 

 nature where these plants are buffeted by the waves, for there has devel- 

 oped an intercalary meristem near the leaf base which becomes active 

 when the blade is removed. Killian ( 1911 ) describes the way in which an 

 injured stem is reconstituted in Laminaria digitata. 



Some of the most remarkable cases of regeneration occur in the fruiting 

 bodies of the fleshy fungi— toadstools, mushrooms, bracket fungi, and 

 similar types. These are formed from masses of tangled hyphae which do 

 not adhere to their neighbors as do cells in higher plants but are merely 

 packed together in a weft of tangled threads. Even so, they tend, if in- 

 jured, to restore the missing portions and produce a normal sporophore. 

 This has been observed in Stereum by Goebel (1908), in Agaricus by 

 Magnus (1906), and in other fleshy fungi. Under favorable conditions 

 almost any part of one of these fruiting bodies will restore portions of its 

 tissues that are removed. Such structures provide promising material for 

 studies in regeneration. Brefeld and Weir maintain that every cell of 

 C&prinus has the potentiality of producing an entire sporophore. 



Among bryophytes, the hepatics regenerate with particular readiness. 

 Early work with these plants has been reviewed by Correns ( 1899 ) . The 



