SCIENCE-GOSSIP. 



145 



A FRESHWATER ALGA. 



By C. E. Britton. 



"IV/riCROSCOPISTS, more especially those who 

 do not neglect micro-botany, are familiar 

 with the most frequent representative of the 

 Florideas, or red "seaweeds," that grow in fresh- 

 water, namely Batraclwsperynum. Yet, as a rule, all 

 observation of the plant is confined to a superficial 

 examination under a low power of the microscope, 

 and ends there. Whereas Batrachospernium, being 

 a good type of the red seaweeds, well repays a little 

 extra trouble devoted to its study, and it does not 

 require very skilful 

 manipulation to see 

 the chief points in its 

 structure, including 

 the apical cell and 

 male and female 

 organs. There are 

 but few good ac- 

 counts in English of 

 this alga. One of 

 the most accessible 

 is that contained in 

 Smithson's "Algas," 

 in the "Young Col- 

 lector" Series; yet 

 the process of fer- 

 tilization described 

 therein as occurring 

 in Batrachospermum 

 is erroneous in many 

 points when looked 

 at in the light of 

 recent researches. 

 An opinion prevails, 

 I believe, that this 

 alga is rare. It may 

 not be common, but 

 it is usually to be 

 found in likely situa- 

 tions, such as wells, 



springs and streams containing much spring water. 

 In ponds and streams not spring-fed it is certainly 

 rarer. When growing the plant has the appear- 

 ance of consisting of short tufts of filaments 

 attached to stones, etc. Its most usual tint is 

 blackish, though the colour is said to range from 

 green, violet, brown to black. Sometimes, when 

 growing under certain conditions, the plant is al- 

 most blanched, very little colouring-matter being 

 developed. This form is most suitable for studying 

 the structure of the plant, and the next best are green 

 and blue-green forms. The surface of the plant 

 is covered by a jelly-like substance, and when 

 gathering the plant, while it is easy to detach it 



^^ 



/ 



"3 



■^o 



Freshwater Alga (Batrachospermum). 



Fig. I, Portion of leaf with antlieridia. An. Fig. 2, Procarp ; 

 T, trichogyne ; C, carpogone. Fig. 3, Cystocarp ; .\, trichogyue 

 and spermatium. 



from its place of growth, on attempting to remove it 

 from the water it has a way of slipping back through 

 one's fingers. Owing to this slimy nature the 

 plant derives its generic name of Batrachospermum, 

 besides which it possesses two gnglish names 

 which are evidently the invention of writers : one 

 being "frog-spawn," a literal translation of the 

 scientific name, the other, "bead-moss," a very 

 inaccurate designation. If an English name is 

 required, I would suggest beaduiort. It is easy to 



see why the name 

 " bead - moss" has 

 been bestowed on 

 the plant, for if we 

 examine a plant, 

 referably with a 

 pocket-lens, we shall 

 notice that it appears 

 to be made up of 

 small dark beads 

 suspended closely 

 together on very 

 fine threads. On the 

 older parts the beads 

 have a squarish or 

 roundish outline and 

 stand apart from 

 each other, and on 

 the younger tapering 

 parts of the branches 

 are more disc-shaped 

 and placed closer 

 together, until near 

 the extremities the 

 bead - like arrange- 

 ment ceases. Em- 

 bedded in many of 

 the bead -like parts 

 may perhaps be 

 noticed small grains 

 of a darker colour, the fruit-bodies or cystocarps. 

 It is very important to notice these, as they give 

 rise to the cells that reproduce the plant, and 

 these latter reproductive cells are the only means 

 of increase that, as far as is known, the mature 

 plant bears. 



For the further study of the alga the use of the 

 compound microscope is necessary, making use 

 first of all of a low power, and then it will be seen 

 that in addition to being one of the most interest- 

 ing of the freshwater alga\ Batrachosf-aininii is one 

 of the prettiest. Under a power, such as a one- 

 inch, the bead-like appearance will be noticed as 

 due to tufts of filaments that arise at intervals in 



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