NOTES AND MEMORANDA 457 



Fam. 2. Scytonemacece Borz. (Sajtonemece Tlir,, Scytone- 

 macece and Sirosiphonacece Eabb.). Filaments filiform, 

 simi^le, or more often branched, interrupted by bctero- 

 cysts ; increase apical and indefinite ; spores. 



Fam. 3. Rrvulariacece Eabb. (Calotrichece Tbr.). Fila- 

 ments filiform, simple or branclied, often with 

 heterocysts ; increase apical and limited ; spores. 



Fam. 4. Oscillartacece Rabh. ex part. {Lynfjhyce Thr.). 

 Filaments filiform, simple, without heterocysts ; in- 

 crease indefinite ; no sjjores. 



Sub-ord. 2. Cystogoneae Borz. Multiplication by means of 

 isolated, immobile, vegetative cells. 



Fam. 5. ChamoesiphoiiacecB Borz. Filaments filiform, 

 simple ; increase apical, indefinite ; no heterocysts ; 

 spores (?). 



Ord. II. GiiCEOGENiE Cohn. Cells distinct, cither isolated or 

 collected into larger or smaller families. 



Fam. 6. Chroococcacece Eabh. ex part. Cells multiplying 

 by indefinite bipartition in three directions, at all 

 events at the moment when the colonies are first 

 formed ; spores. 



The paper referred to contains an exhaustive account of the 

 biology and morphology of the first of these families, the Nostocliacew, 

 under which Borzi includes the following genera :—Nostoc Vauch., 

 Anahcena Kiitz., Isocystis Borz., Sjohcerozyga Elfs., Cylindrospermum 

 Elfs., Nodularia Mart., and Aphanizomenon Morr. 



In a subsequent paper in ' Flora,' * Sig. Borzi makes some further 

 remarks on his proposed new genus Isocystis, of which he gives the 

 following character : — Filaments solitary, a larger or smaller number 

 irregularly and more or less densely interwoven into an indefinitely 

 extended layer, never united in parallel growth, often very delicate and 

 perceptibly narrowed at the apices ; cells elliptical or spherical, some- 

 times oblong-quadrate from mutual compression, sometimes angular or 

 disk-shaped, closely connected or distinct ; spores, where known, glo- 

 bose, sub-globose, or oval, of a bluish-olive or dusky golden colour ; 

 exospore thin or moderately thick, very smooth or scabrous. The 

 typical species is very similar in external appearance to an Anabfena, 

 but is distinguished by the invariable absence of heterocysts, and by 

 the tendency of the filaments to unite into small bundles, like those of 

 Aphanizomenon. The genus includes four species, three of them 

 now described for the first time, the fourth previously regarded as an 

 Auabseiia (A. infusionmn). They represent the simplest and lowest 

 type of the Nostochaccfe, scarcely ever forming colonies of any 

 considerable size. The very delicate moniliform filaments are found 

 floating on the surface of the water, either solitary or in interwoven 

 masses ; the mucilage which envelops them is very small in quantity, 

 and disappears completely at a very early period. Borzi considers 



* ' Flora,' xxxvi. (1878) 4G5. 



