ZOOLOaY AND BOTANY, MICROSCOPY, ETC. 391 



cell-sap. They are all coloured brown by alcoholic solution of iodine, 

 and show the other ordinary reactions of proteinaceous crystalloids. 

 They occur most abundantly either in very large-celled Ah'te like 

 Cladophora and Griffithsea, or in those the vegetative thallus of which 

 is unicellular, as Acetahularia, Bryopsis, Codiiim, and Dasycladus ; 

 their size and number being apparently dependent on the size of the 

 cells in which they occur. They appear to result from the develop- 

 ment in the cells of an excess of proteinaceous substances. In some 

 instances, as Acetahularia, where they are found only in specimens in 

 which there are no spores, they are used up in the formation of the 

 spores. 



Ehodospermin has been observed by Cramer and Cohn in Bornetia 

 secundiflora, Callithamnion caudatum, C. seminudum, and Ceramium 

 ruhrum, in which Alg^e it is formed by the long-continued action of 

 the reagents named. What appear to be immature crystalloids of 

 rhodospermin have also been detected by Klein in specimens similarly 

 treated of Griffithsea phyllamphora and Phlebothamnion versicolor. 



Phyllosiphon Arisari.* — This organism, parasitic on the leaves 

 of Arisarum vidgare in Italy, was first observed and described by 

 J. Kiihn, who regarded it as a Siphonaceous Alga allied to Vaucheria. 

 Schmitz has also investigated it, chiefly in reference to its multi- 

 nucleated cells, and considers it to be a fungus constituting a special 

 group of the Phycomycetes. L. Just has now undertaken a complete 

 investigation of its structure and life-history. 



The parasite causes well-defined light-green or yellowish patches 

 on the leaves and leaf-stalks of the host, each patch being inhabited 

 by a single individual, which attacks the intercellular spaces only. 

 Each individual consists of a single entirely undivided but often 

 much-branched interwoven hypha, averaging about 0*05 mm. in 

 diameter. 



The young apices of the branches contain no chlorophyll, but a 

 colourless protoj^lasm rich in larger or smaller granules (microsomes) 

 and containing vacuoles and drops of oil. Further from the apices of 

 the branches, the hypha is gradually more and more deeply coloured 

 by chlorophyll, and contains a larger quantity of oil. When the 

 spores are about to be formed, a parietal layer of protoplasm becomes 

 nearly homogeneous, and comparatively free from oil-drops, while a 

 layer of protoplasm next to this gradually breaks up into numerous 

 minute portions, which clothe themselves with cellulose-coats, and 

 develops into the spores. The innermost central portion of the 

 protoplasm is rich in oil, but contains comparatively few granules 

 and no chlorophyll ; it absorbs water greedily and swells up. The 

 escape of the spores takes place from ten to fourteen days after tlie first 

 appearance of the patches. Just confirms Schmitz's statement of the 

 occurrence of a large number of nuclei in the hypha) ; but he did not, 

 like Schmitz, at a subsequent stage find one in each spore ; the spores 

 are entirely destitute of nucleus. 



The spores are of oval form, averaging about 5 ;m in length and 2 • 5 /a 



* Bot. Ztg., xl. (1882) pp. 1-8, 17-2G, 33-47, 49-57 (1 pi.). 



