108 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



to be resting-cells similar to those of Conferva pachyderma. The 

 immotile reproductive cells, whicli are formed directly vidthout auy 

 true process of cell-formation, he calls " akinetes " ; while to those 

 formed asexually by true cell-formation he gives the term " aplano- 

 spores " ; they germinate directly, or after a period of rest, tinder 

 cultivation Trentepohlia umhrina may become quite green. 



Other species of the pseudo-genus Gongrosira, Wille refers as 

 conditions of species belonging to different genera as follows: — 

 G. dichotoma Kiitz., is a peculiar aplanospore condition of Vaucheria 

 geminata Walz. ; G. clavata Kiitz. is the sporiferous vegetative plant 

 of Botrydium granulatum ; G. ericetorum Kiitz. is the protonema of a 

 moss ; G. ericetorum v. suhsimplex Rab. is probably a TJlothrix or 

 Conferva ; G. pygmcea probably a Stigeoclonium ; G. Sclerococcus Kiitz. 

 (Stereococcus viridis Kiitz.) may be a Trentepohlia ; G. protogenita'Kvitz. 

 is probably the palmella-form of a Stigeoclonium ; Eeinsch's species 

 cannot be determined; G. onusta 7iQ\\. comes near Trentepohlia de 

 Baryana. 



Phyllosiphon Arisari.* — M. Franke finds this parasitic alga 

 abundantly on the leaves of Arisarum vulgare in the neighbourhood of 

 Messina, and elsewhere in Sicily and Calabria ; but it appears never 

 to attack A. italicum. The spores are capable of germinating at any 

 period of the year, but must go through a period of rest ; the larger 

 spores appear to divide into several. They always attack their host 

 by penetrating the epidermis between two cells, which they force 

 apart by their germinating filament. The restricted conditions 

 necessary for the germination of the spores greatly diminish its de- 

 structive effects. 



Occurrence of Crystals of Gypsum in the Desmidiese.f — The 

 occurrence of crystals of calcium sulphate, endowed with a peculiar 

 " dancing " motion, has long been known in the terminal vesicles of 

 Closterium and in other desmids ; the phenomenon has now been care- 

 fully investigated by A. Fischer. Their chemical constitution was 

 clearly established by different tests. They are always quite isolated 

 from one another, and occur in all parts of the cells, though in the 

 greatest quantity in the terminal vesicles ; they are either carried 

 along passively by the currents of protoplasm, or they " swarm " in 

 the space filled with cell-sap between the cell- wall and the radiating 

 chlorophyll-bodies ; these vesicles are not true vacuoles, but portions 

 of the cell-sap space. The crystals are not formed, nor do they grow, 

 in this vesicle, but reach it in a mature condition from some other 

 part of the cell, being formed apparently in the furrows between the 

 bands of the chlorophyll-bodies ; from here they are carried to the 

 terminal chambers by the protoplasmic currents. 



Fischer found these crystals in all the species of Closterium which 

 he examined ; also in various species of Cosmarium (though individuals 

 are often entirely destitute of them), their form being the same as in 

 Closterium. They occur also in Micr aster ias, Euaslrum, in which 



* JB. Schles. Gesell. Vaterl. Cult., 18S3, pp. 195-7. Cf. this Journal, ii. (1879) 

 p. 606 ; ii. (1882) p. 391 ; iii. (1883) p. 108. 



t Pringsheim's Jahrb, f. Wiss. Bot., xiv. (1883) pp. 133-84 (2 pla.). 



