Kelley 



— 122- 



Mycotrophy 



Normal renewal of growth in mycorrhizae of Taxus was described 

 and figured by Prat (1926): "'Mamelons" formed during one 

 season are quiescent over winter but "Au printemps, les cellules du 

 meristeme central se remettent a proliferer, formant un massif qui 

 traverse les assises externes comme fait une radicelle pour les tissus 

 de la racine-mere. A I'interieur de ce massif apparait un nouvel 

 endoderme qui se raccorde a I'ancien. L'ecorce du nouveau segment 

 de racine est done separee de I'ancienne ecorce par des assises de tissus 



Fig. 8. — Renewed growth of a mycorrhiza of 

 Pinus virginiana, showing splitting of mycoderm 

 and extension of root-tip (Collected near Balti- 

 more, 22 February 1930). 



morts et pigmentes." This is the method of formation of "pearl- 

 necklace" beaded mycorrhizae. 



Ectotrophic vs. Endotrophic: — Mycorrhizae have been con- 

 ventionally classified as ecto- and endotrophic, the distinction originat- 

 ing with Frank (1887) who said: "We (may) designate all those 

 forms as 'ectotrophic' which have the nourishing fungus external 

 to itself, and as 'endotrophic' where it (the fungus) penetrates into 

 the interior of certain root-cells." But with passing years doubt was 



