r)46 



THE PATHOGENIC ALGAE. 



but several inhabit nqxdicac, chiefly species of Anthoccros, Blasia, 

 Piilia, Aneura, Diplolaena, Sauteria, and Biccift. 



Nostoc lichenoides Vauch.^ is a common endophyte in the 

 mucilage-cavities of Anthoceros laevis. The motile algal filaments 

 gain admission through the stomata or mucilage-fissures on the 

 lower side of the thallus. Onl}'- one filament is admitted into 

 each cavity, then the opening is closed by an increased turgescence 

 and growth of the guard-cells ; the imprisoned Nostoc nmltiplies 

 to form a colony. 



Leitgeb states that after infection has successfully taken place, 

 and frequently before the stoma has quite closed, the guard- 



FiQ. '6iZ.— AiKibiiij-aa azuilae. Longitudinal section througli tiie posterior lobe 

 of a floating leaf of Azolla airoliniana. The cavity is filled with lYosioc-filaments 

 and septate hairs. 



1, A septate hair, and a filament of Analnuna. (v. Tubeiif del.) 



cells divide and ultimately form a three-layered covering of 

 cells over the intercellular space. Simultaneously all the thallus- 

 cells round the infected cavity undergo radial division and grow 

 into the cavity, first as papillae, then as much-branched and 

 septate tubes of various lengths ; the space left between them 

 becomes meanwhile filled with the Nostoc. In the case of 

 Anthoccros Icievis the tubes form a kind of pseudoparenchyma 



^Bibliography. Janczewski, Botan. Zeituixj, 1872, ami Annales d. aci. 

 natur., Ser. 5, xvi. Milde, Botan. Zeihing, 1851. Leitgeb, Akadcmie d. Wissen- 

 schaften in Wien, 1878; also Uii.tersuchungen iiher Leherinoose, I. Goebel, "Die 

 iMuscineen," in Schenk's Haudhuch d. Botanik, 1882. 



