ABSTRACTS. 57 



ABSTRACTS. 



Note on the Occurrence of Bracliiomonas sp. 

 By W. Xeilson Jomes, M.A., F.L.S. 



[Read 1st December, 11)21.] 



The sudden nppearance of many of the simpler algse iu a locality 

 and their equally suddeu disappearance from it is a well-known 

 phenomenon. The present coninumication deals with a mysterious 

 visitation of this kind, which is worth putting on record on account 

 of the rareness of the species in question and of the unorthodox 

 conditions under which it was found growing. 



Brachiomonas is a unicellular green alga belonging to the sub- 

 family Chlamydomonadece of the family VolvocineiB. It it charac- 

 terised by possessing a cell-body furnished with four regularly 

 disposed hollow lateral horns, each of which is curved backwards, 

 and a fifth posterior horn whicli is straight. At the apical end 

 are two long cilia arising from a slight wart-like protuberance. 

 The nucleus is situated anteriorly ; a large pyrenoid is present 

 towards the posterior end. The chloroplast appears, in most cases 

 at least, to extend not quite to the tips of the horns : this is 

 specially noticeable in the posterior horn. The proto[)lasm, how- 

 ever, extends to the distal end of each horn. Reproductioti takes 

 place (1) by the formation of four zoospores within the body of 

 the mother-cell, which retains its motility up to the moment that 

 the zoospores are liberated — or even a little longer; (2) by the 

 formation of gametes of smaller size than the zoospores, 16 in each 

 mother-cell, which conjugate in pairs to form a resting zygote. 

 The organisms progress forward with a somewhat jerky move- 

 ment, rotating about their longitudinal axes. 



The botany garden at Bedford College possesses, among other 

 possible locutions for algae, a small lily pond about 2 feet deep 

 ami a winding " ditch " of varying depth. The latter, ow ing to 

 defects in the concrete, had been allowed to dry out in the summer 

 of 1920 preparatory to repairs being carried out : in May 1921 

 it was for the most part dry, although some of tlie deeper parts 

 still contained water. 



During May, material of Clamydomonas was required, and 

 samples of water were collected from the garden and examined in 

 the laboratory. In three cases the water was found to contain 

 an ahnost pure culture of Bracliiomonas. In every case these 

 samples had been taken from sliallow pools formed in the ditch 

 by recent rain — the lily pond and the deeper pools showed no 

 evident signs of the alga. 



The appearance of this plant in London becomes the more in- 

 teresting when its known distribution is considered. So far as 

 I have ascertained, there are recorded in the literature only three 



