QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 295 



may be effected by certain cells persisting as " innovation- 

 cells/^ and growing into adventitious buds next year, or the 

 apical cell of the old bud continues unaltered during the 

 vegetation- pause to eventually resume its growth. 



iii. Sphacelaria olivacea, Dillw., shows in the structure and 

 development of its stem and branches no essential differ- 

 entiation beyond that of size; the latter are, without excep- 

 tion, products of the joint-cells. The unilocular sporangia 

 occur on the smaller branches, whose terminal cells, as in 

 Cladostephus, swell up directly to form them ; the supporting 

 cell also grows through, but gives rise, not to a new spo- 

 rangium, but to a new branch. Besides these certain lateral 

 branches, shorter than the merely vegetative, modify their 

 terminal cell into globular sporangia, whose contents become 

 divided into cubical cells. Pringsheim has reason to think 

 that the zoospores in the unilocular sporangia arise in a 

 transitory cell-net. Hence he is led to the conclusion that 

 the difference between the two sporangial forms in the Phce- 

 osporea is not an absolute one, but only expresses a different 

 degree of persistence in the mother- cell-tissue; consequently, 

 this second form of sporangia in S. olivacea may be com- 

 parable to multilocular sporangia. S. olivacea would there- 

 fore seem to be a species in which the definitive separation 

 of the two sporangium forms is not yet fixed, but only about 

 to be originated. 



Other asexual modes of increase occur. Amongst these 

 are the three- four-rayed gemmae (Brutknospe). These, as 

 regards position, structure, and morphology, are manifestly 

 metamorphosed fruit-branches; they fall oflF, grow to new 

 plants, and are thus comparable to the gemmae of mosses and 

 liverworts. After separating from it, their supporting cell 

 grows out again, to produce a cell higher up than the last, a 

 new gemma. — W. Archer. 



4. Batrachospermum. — Sirodot {' Comptes Reudus/ May 

 and June, 1873) finds that Chantransia is an asexual gene- 

 ration, which is developed from the sexually produced spores 

 of Batrachospermum. 



5. Parasitic Alga. — Kny {' Sitz. der Gesellsch. Natur. 

 Fr. zu Berlin,' Nov., 1872) describes two additional instances 

 of algae with a parasitic habit. On examining, in September, 

 1872, at Heligoland, decayed specimens of Delesseria san- 

 guinea, of which the fronds had to a great extent decayed, 

 leaving only the midribs beset with adventitious sprouts, he 

 met with examples showing abnormal brown bands and spots. 

 On making thin superficial sections through these portions 

 he found that they were covered by an irregular network of 



