ALG.^. 87 



•which spftlo down and devclopp a cellulose coat, whilst the further development 

 of the smaller is uukuowu. 



NOSTOCHiyiE.T.. 



Plants growing on damp moss or earth, and on stones in freshwater. They consist 

 of slender moniliform tranquil or oscillating filaments, composed of cells placed end to 

 end, immersed in a dense gelatinous matter, formed hy tlie fusion of the gelatinous sheaths 

 of the filaments. Eeproduction by cell division. 



Tliis order embraces seven genera — JVbstoc {Hormosiphon), Aphanizomenon, 

 Sphterozi/ga, Anahania, Spermoscira, Trichodesmium, and Monormia. 



A group of obscure phmts, resembling Cvlleina amougst Lichens, found all over 

 the globe, even on ice or snow, often occurring in detached masses. Monormia forms 

 floating jelly-like masses on brackish water, sometimes of great extent. 



JVostoc ediile is sold in China dried, and is \ised as an ingredient in soups. 

 Trichodesmium Ehrenbergii resembles chopped straw, and floats on the ocean, and also 

 on the surface of the lied Sea. 



OSCILLATOEIEJE. 



Plants growing in fresh and Irackish pools, hot springs, rivers and vegetable infusions. 

 They are formed of transversely-striated /laments, sometimes spirally curled or sheathed in 

 mucus, crhibiting a serpentine motion. Reproduction by transverse division. The order 

 embraces fourteen genera : Oscillatoria, Vlothrix, Unactis, Spirulina, Calothrix, 

 Leptothrix, Microcohus, SclerotJirix, bacterium, Lyngbya, Rivularia, Vibrio, Scytonema, 

 Olaotrichia. Vibrios are minute, colourless, active, jointed bodies, that abound in 

 decomposing infusions, and like the still simpler Bacteria, which are mere inflexible 

 rods, are pi'obably rudimcntaiy states of other Alga. 



The knowledge that the presence in the blood of man and animals of microscopic 

 rod-like bodies in various diseases, each disease having its concomitant and distinguish- 

 able organism, is likely to prove of practical advantage. For example, a horse is 

 attacked with certain symptoms, which may be of no dangerous import, or may be the 

 forerunner of the dangerous and highly contagious disease, termed ' Ludifina,' in 

 Northern India. A di-op of blood drawn from the sick animal is placed under the 

 microscope, and if the organisms which are associated with the disease 'Ludiana' 

 arc seen to be present in the blood, the horse is at once slaughtered and buried, 

 thereby probably arresting the spread of the disease to other animals ; but if these 

 organisms are not visible, the animal is simply watched, and may eventually prove 

 to be only suffering from a trifling or curable ailment. 



ALG^ (Proper). 

 Cellular acotyledonous plants, aquatic or growing on damp ground, always 

 exposed to the light. Reproduction either asexual by means of zoo.^pores, or by means 

 of uiUheridia and sporantjia, monoecious or dioecious, and mostly producing motionless 

 spores solitary or quaternary in the same sporangium. 



True Algce are divided by Decaisne into six orders, some of the lowest forms, 

 however {Diatomecc), have been referred to the animal kingdom. 



DIA TOMIEJ'.. 



Microscopic organisms living in fresh or salt water, generally prismatic and rect- 

 angular, free, sessile, or pedicelled, naked, or immersed in mucilage, and divided into 

 polymorphic fragments {frustulcs). The envelope is rigid, siliceous, two-valved, and 

 finely striated. 



Besides their multiplication by spores (as in Desmidiea) Diatomiea; arc reproduced 

 by fissunng. On the centre of each frnstule, in the solitary species, and of each 

 segment or joint in the aggregated forms, there is frequently visible on the young 

 Diatom a line dividuig it into two (or more) frustiih's, which become distinct and 

 similar individuals. Certain species are parasitic ; others form flakes or gelatinous 



