59 



from out of which aj^parently issues a dehcate setaceous fila- 

 ment of considerable length. These setae are not always met 

 with, and I should say are rarely seen in mounted specimens, 

 as they are extremely caducous. It is these setaceous filaments 

 which place this remarkable plant in the family Chsetophor- 

 acese of the Confervoid Algae, and at the same time would 

 appear to ally it to the Bulbochaete, with which genus Hassall 

 considers it has close affinities. 



On the specimens on Slide 'No. 2, which were taken from 

 the stem of a water plant, there will be noticed on the back 

 of the cells nearer the margin than the centre, several masses 

 of Eudochrome. These are the Sporangia. The reproduction 

 of the plant is said to be effected by zoospores as well as spores, 

 the zoospores being produced singly from the cell contents 

 and bearing two cilia. With plants so minute, observation 

 in respect of the reproduction by zoospores is extremely diffi- 

 cult, and it is but rarely, indeed, that such points can be 

 noted,and only when one is so fortunate as to have a specimen 

 under examination in which the zoospores are on the point of 

 escaping from the cells. This is quite possible when the plant 

 grows in an aquarium, through the sides of which it may be 

 observed with a glass from day to day. 



Dr. Grray describes the organism as follows : — " The form is 

 discoidal, circular, slightly concave on one side, formed of very 

 minute, nearly equal sized square cells, placed on forked lines 

 regularly spreading from a central cell to the circumference ; 

 the frond is thin, membranaceous, and the upper and under 

 surfaces are similar. The fructification consists of from twelve 

 to sixteen square thickened patches, forming a circle (some- 

 times two) rather nearer the margin than the centre of the 

 disc, the square patches being often placed in pairs. The 

 fructification was first observed by Suringar in his thesis 

 entitled " Observationes Physiologicae," delivered in Ley den, 

 3rd March, 1857." 



This description fails to include the setigerous sheaths, 

 which is an important omission, being that part of its organisa- 

 tion above others which has enabled botanists to give the 

 genus its natural position. 



The sheath and filament are well shown on a specimen in 

 preparation No. 2, where the delicate filament will be seen 

 to issue from the setigerous sheath for a length almost equal 

 to the diameter of the frond ; and in both of the preparations 

 (Nos. 2 and 3) of the plant taken from the natural habitat 

 there can be seen, with a little management of the light, 

 numerous sheaths. Specimen No. 1 grew on the glass side of 

 an aquarium, and it will be noticed how much finer the frond 

 is than in those taken from the stems of water plants, so much 



