546 



THE PATHOGENIC ALGAE. 



but several inhabit Hcpaticae, chiefly species of Anthoceros, Blasia, 

 Pcllia, Anet/ra, Diplolaena, Sauteria, and Riccia. 



Nostoc lichenoides Vauch. 1 is a common endopbyte 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. Only 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 multiplies 

 to form a colony. 



Leitgeb states that after infection has successfully taken place, 

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



Fio. 323. Anabaena azollae. Longitudinal section through the posterior lobe 

 of a floating leaf of Azolla caroliniana. The cavity is filled with Aostoc-filaments 

 and septate hairs. 



1, A septate hair, and a filament of A milieu: wt. (v. Tubeuf 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 Nostnc. In the case of 

 Anthoceros laevis the tubes form a kind of pseudoparenchyma 



1 Bibliography : Janczewski, Botan. Zeittuig, 1872, and Annales d. ..sn. 

 natur., Ser. o, xvi. Milde, Botan. Zeitung, 1851. Leitgeb, Akademie d. Wissen- 

 schaftKii in Wien, 1878; also Untersuchungen iiber Lebermoose, i. Goebel, "Die 

 .Muscineen," in Schenk's Handbuch d. Botanik, 1882. 



