\ i ALGALS. 



clouds or darkness the reverBO. It usually takes place at the earliest hours of the 

 morning] in Vaucheria about 8 a.m., iu Cutleria at daybreak. Euteromorpha 

 clatlir.au i- the only kind that has been seen to emit them in the afternoon. A high 

 temperature is unfavourable, moderate warmth promotes the phenomenon; this is 

 shown by the rapidity with which Algals brought into a warm room emit their 



sooepi 



// ,>;,, n of the. y,, i ;,,,/.— The movement of zoospores generally lasts only a few hours, 



and seldom conti l beyond the day on which they are emitted ; sometimes, how- 



01 In i>: sonata, several remain active even on the third day. Motion is 



suddenly arrested by alcohol, ammonia, acids, iodine, &c. ; the latter colours them 



brown, which renders it more easy to perceive their cilia?. 



Tifir Rilalion t» Infusoria. — M.'Thuret wholly denies their identity with or muta- 

 bility into animalcules. He points out their resemblance to the common Diselmis 

 viridia, (or Chlamydomonas pulvisculus) which renders ponds green; and he believes 

 that when the Diselmis has become attached to the edge of a vessel, and is motionless, 

 assuming a spheroidal figure, that it has been confounded with germinating zoospores. 

 If' regards it as probable that observers have confounded all manner of microscopical 

 globules, however different from each other in their nature; and that infusoria, 

 zoospores, the spores of mosses, the green gonidia of lichens, &c, all regarded as the 

 same thing, have given rise to the notion that one kind of Alga could not only produce 

 a different species, but even a moss, a liverwort, or a lichen. The reader is requested 

 to consult M. Thuret's important memoir in the Annates des Sciences Naturelles, sSr. 3, 

 vol xiv., or his Recherches sur les Zoospores des Ale/toes et les Antheridies des Crypto- 

 gamet, (Paris, 1851,) and the admirable plates which accompany the treatise. 



This author proposes to divide algals into two primary groups, of which one is 

 propagated by zoospores, and the other not. The zoosporous part he arranges thus : — 



Zoosi'oui.i; Decaiane (exclusive of Nostochineae, Rivulariese, Oscillatoriese, Pal- 

 nielleas, Lemanea?) — Aplosporece Decaisne (exclusive of Batrachospermea;, Fucaceae, 

 and somo Dictyoteac). 



§ 1. Chlorosporeae. Colour, usually green. 



Bryopsidere ; Confervea; ; Draparnaldieao ; Ulvacea? ; (Edogonieae ; Vaucherieae ; 

 Saprolegnieea ; Derbesiese; Spougodiea?. 



§ 2. Pheosporeae. Colour, hrown or olive. 



learpesa : Mvrionemeae ; Chordariea? ; Sporochneae ; Punctarieae ; Dictyo- 

 siphonese; Scytosiphonese; Laininarieae ; Cutlerieae. 



That these zoospores are the means by which Algals are propagated seems to be 

 proved by the following experiment made by Stackhouse, and recorded in his Nereii 

 Britannica ; 



" I laving procured a number of wide-mouthed jars, together with a siphon to draw 

 off the water without shaking or disturbing it, on Sept. 7, 1796, I placed my plants 

 (F. serratus, canaliculatus, and tuberculatus,) carefully in the jar, with their bases 

 downward-;, as in their natural state; on the following morning I decanted off the 

 water, and. letting it subside in the basin, I found a few particles at the bottom, 

 which, on being viewed with the microscope, appeared to be little fragments detached 

 from the surface by friction in carriage. I then poured a fresh quantity of sea water 

 on the plants, and placed them in a window facing south : on the following morning 

 the jar containing the plants of F. canaliculatus discharged into the basin a few 

 y.ll,, wish grains, which, on examining them, I found to be the actual seeds of the 

 plant ; they were rather oval than pear-shaped, but the most curious circumstance 

 tiding the observation was. that each individual seed was not in contact with the 

 •r, but enveloped with a bright mucilaginous substance. It was easy to guess the 

 wise economy of nature' in this disposition, which, as hinted above, serves a double 

 purpose; each equally necessary towards continuing the species. On the following 

 """'"'"" i '' quantity of seeds were discharged by this plant, and at this time a 



lew seeds were procured from F. serratus; but this latter plant discharged such a 

 quantity oi mucous fluid that the sea water in which the plant was immersed was of 



e consistence of syrup, and consequently, the seeds being kept suspended, it was 



Oifflcult to separate them. The seeds of F. canaliculatus, however, were numerous, 



and v.-iMe to the naked eye, and after letting the water rest for a few minutes it was 



o difficult matter, by gently inclining the basin, to pour off the water and let the 



teds remain. In performing this operation I was witness to an explosion or bursting 



