122 NATURAL SCIENCE. Feb., 



fatal. A few other Fungi, such as certain parasites on Zostera, a 

 marine flowering plant, have been recorded with some doubt so far 

 as their actual growth in sea-water is concerned. 



This parasitism of Fungus on Alga naturally suggests the case of 

 the lichens, where, however, both classes of organisms dwell together 

 in amity and their relations are symbiotic rather than parasitic. 



Professor Perceval Wright (i8) described in 1879, in an admirable 

 paper, " a new species of parasitic green Algae belonging to the genus 

 Chlorochytnum of Cohn," whicli he found inhabiting the fronds of 

 Schizonema, PolysipJionia, &c. A consideration of this form opens fresh 

 ground, since it, like the type form of Chlorochytriinn, inhabiting duck 

 weed, described by Cohn (19) in an interesting paper on parasitic Algae, 

 does not appear to be a case of true parasitism, but rather of that sort 

 called by Klebs " Raumparasitismus," in which the host furnishes 

 merely lodging without board to the intruder. There are many such 

 cases among the lower Algae, and their bearing on symbiosis and 

 on the parasitic habit itself is an instructive one. A large number of 

 Algae (especially marine forms) live as epiphytes on larger Algae, and, 

 indeed, constantly select the same species of host and the same part 

 of its thallus. Many of these deserve special investigation, since cases 

 occur in which the rhizoids of the epiphyte (and even wedges of its 

 tissue, like haustoria) penetrate the host, and if not actual burglars are 

 certainly in a very compromising position. We have an example of 

 more than mere " Raumparasitismus " (we thank Klebs for that word) 

 in Phyllosiphon arisari, a siphoneous Alga which lives in the intercellular 

 spaces of the \ea.ioiAnsaruin vulgare and even consumes the chlorophyll 

 in the adjacent cells. Other Algae are known to inhabit the tissues 

 of flowering plants, of Azolla and of Muscineae, but the considera- 

 tion of these is at present leading us away from the subject. Chloro- 

 chytyiuni (which may be put among the Protococcaceae) furnishes us at 

 any rate with a case of symbiosis, so far as shelter is concerned, 

 between Algse, and the line of investigation so successfully pursued 

 by Professor Perceval Wright is one that phycologists may be confi- 

 dently incited to follow. 



Finally, and of special interest, are certain tubercles on the 

 fronds of Florideae described last year by Dr. Schmitz (20) as caused 

 by Bacteria. The numerous cases of error in attributing the causes 

 of diseases to Bacteria may make one unduly cautious in accepting 

 statements of this kind when the possibility of the Bacteria being 

 merely post hoc has not been absolutely excluded by the evidence 

 of inoculation experiments. Dr. Schmitz, however, is not the man 

 to make rash statements, and his research is a very noteworthy one, 

 and one, moreover, that suggests other matters of interest in regard to 

 Bacteria, 



I am convinced that the subject of the parasites of Algae — as well 

 as that of parasitic Alga^ — is but in its infancy, and in the hope that 

 workers may be attracted to a field of research of great difficulty. 



