MYCOIDACEAE. 553 



Where this occurs, black patches are frequently formed so that 

 the leaves become spotted, but the injury to the host-plant is by 

 no means so severe as in the following species. 



Ceph. parasiticus Karsten. This species is common on the 

 leaves of Ccdathea and Pandanus at Buitenzorg. It spreads 

 through the whole leaf-tissue blackening and killing it. The 

 epidermis is blistered and its cells filled with the alga ; ultimately 

 the cuticle is ruptured and the stalked sporangia are pro- 

 duced. The swarm-spores germinate in the stomatal cavity, 

 or in the adjacent intercellular spaces. 



Ceph. minimus Karsten is parasitic on leaves of Zizyphus 

 Jujvha at Buitenzorg. It permeates the leaf-parenchyma and 

 kills it, the cells after death becoming completely occupied 

 by the alga. 



Phyllosiphonaceae. 



Phyllosiphon arisari Kuhn.^ This is a true parasite as yet 

 observed only on Arisarum vulgare in Italy and the South of 

 France. It causes death of the leaves and is frequently very 

 abundant. 



The thallus consists of unicellular, non-septate, much branched 

 filaments containing chlorophyll, and filling up the intercellular 

 spaces of the spongy parenchyma of the host. The wall of 

 the filaments gives the reactions for cellulose and consists of an 

 outer and a later-formed inner layer, the latter capable of swelling 

 very much to assist in ejaculating the spores. The chlorophyll 

 corpuscles at first contain no starch, only oil, which, however, 

 decreases during spore-formation, while the starch increases. 

 The spores (aplanospores) are formed inside the algal threads, 

 and are ejected with great force from the extremities of filaments 

 which lie under stomata, and therefore in the position where least 

 resistance is offered to the swelling inner wall. Chlorophyll is 

 not present in the young filaments, but it appears in the older 

 parts, especially about the time of spore-formation, and seems 

 to be stored in the spores. The spores have a nucleus and 

 chlorophyll disc. They germinate to a filament which grows 

 between two epidermal cells into the intercellular spaces of the 

 leaf 



^ Kuhn, " Eine neue parasitisehe Alge," Sitzungsber. d. naturforsch. Ges., 

 Halle, 1878 ; Just, Botan. Zeitung, 1882 ; Schmite (idem). 



