ZOOLOaY AND BOTANY, MICKOSCOPY, ETC. 407 



cliromatophore, and then may ultimately completely replace it, or are 

 formed only on the surface of the pyrenoids. Both modes may occur 

 in the same chromatophore. 



The starch-grains of Florideae differ from ordinary starch-grains 

 by the brown or red colour imparted to them by iodine. Their mode 

 of formation is also peculiar, being produced not inside but outside 

 the chromatophore. In the Phaeophycese starch-grains are formed, as 

 in the Florideae, around the chromatophore, but they are not coloured 

 at all by iodine. 



The " paramyl-grains " of Euglena and similar organisms are 

 chiefly distinguished from ordinary starch by not being coloured by 

 iodine ; they are produced, like the starch-grains of red and brown 

 alg^e, outside the chromatophore. They form a closed envelope 

 round it, completely resembling that of true starch-generators. The 

 pseudo-starch-generators of certain Florideae, e. g. the Nemalieae, have 

 the same origin. 



In some chromatophores the starch is replaced by substances 

 soluble in alcohol, occurring in the form of small drops on the 

 surface, never in the interior. They may also occur in addition to 

 starch. 



Finally, the author compares the chromatophore with the celL 

 nucleus. Both are composed of a reticulate framework, closely 

 resembling protoplasm in its properties. The nucleoli, or inclosures 

 in the nucleus, agree in their reactions and behaviour with the 

 pyrenoids of many algae. Both arise only by division, never by 

 rejuvenescence. ISTuclei and chromatophores may be regarded as 

 two series springing from a common origin, but developing afterwards 

 in different ways to adaj)t them to different biological functions. 



Phycoclironiaceae.* — Proceeding with his detailed account of the 

 Phycochromace^, A. Borzi now describes the two families Eivula- 

 riaceae and Chamaesiphonaceae. The former consists of the following 

 genera: — Calothix Thr,, Sacconema nov. gen., Leptochcete nov. gen., 

 and Mivularia Koth. The two new genera are thus described: — 



Leptochcete. Trichomata simplicia, saepius tenerrima, erecta, 

 thallum indefinite crustiforme, tenue, j)lerumque late effusum ef&- 

 cientia ; heterocystis nullis. Multiplicatio hormogoniis et conidiis 

 chroococcoideis ex articulorum basalium transmutatione ortis. Three 

 species : — L. Crustacea, fonticola, and parasitica. 



Sacconema. Trichomata irregulariter caespitoso-aggregata, 2-plura 

 vagina communi fuscescente, lamelloso-stratificata, valde ampliato- 

 saccata, demum apice soluta, involuta et thallum exiguum gelatiuosum 

 laciniato-lobulatum constituentia ; pseudo-ramulis brevibus, monili- 

 formibus, discretis, heterocystide basilari globoso instructis ; sporis 

 aureo-fuscis, articulos vegetativos duplo superantibus, exosporio cras- 

 siusculo, scabro. One species : — S. rupestre. 



The new family of Chamaesiphonacege consists of the genera 

 ChamcBsiphon A. Br., Clastidium Kirchn., Cyanocystis nov. gen., and 

 Dermocarpa Crouan. It has the following diagnosis : — 



* Nuov. Giorn. Bot. Ital., xiv. (1882) pp. 272-315 (2 pis.). 



