209 



NOTE ON BOTRYDIUM GRANULATUM (L.) GREV. 



By James Burton. 



{Bead November 227id, 1910.) 



Early in October I came across this little plant in immense 

 numbers at the Welsh Harp reservoir, Hendon. Tlie water 

 had been partially drained away. On the right-hand side of 

 the road going from Cricklewood there is normally a considerable 

 body of water which reaches from the road, under the Midland 

 Bailway viaduct and some distance beyond. This space was quite 

 drained, except for the narrow stream of the Brent running 

 through it ; and on the left of the road there was also a large 

 space of partially dried mud. All this, which must amount 

 to many acres, was a distinctly bright-green colour. I went 

 down to the side of the space, and at once noticed the presence 

 of the Botrydium. I walked round as far as possible on the 

 mud and on both sides of the road ; everywhere that I could 

 reach the ground was thickly covered with it. The mud was 

 drier and cracked in some places, and the little plants extended 

 over the edge of the cracks, and were often so closely packed 

 as to leave httle space between them, and had thus become 

 misshapen through mutual j)ressure. I do not think it is par- 

 ticularly rare, but, at the same time, cannot be very common ; 

 I have looked for it for many years without success, and duiing 

 the last two seasons on our Quekett excursions have been careful 

 to search in the most likely places, yet have never found it. 

 It is well known that when it does appear there is almost 

 always, as in this case, a remarkable profusion, and the avail- 

 able area becomes thickly covered. 



The plant consists of small green balloon-shaped vesicles of 

 various sizes, from quite small up to about 3 mm. in diameter, 

 so it is hardly microscopic. Below the surface of the mud an 

 extensive root system is produced ; the roots branch dichoto- 

 mously, and extend to a considerable distance, often reaching a 

 length of I inch. As the plants grow very thickly, the roots 

 are entangled and interlaced, and the whole plant being of 



