MYCOLOGIC FLORA OF KEW GARDENS. 447 



not suit the species, and so limits its distribution in much of the 

 intervening space. Practically I find it impossible to grow certain 

 species of pond-weeds — F. 'poUjfjonifolms, for example ; they linger 

 for a time and then die away, and these are just the species which 

 we ought to find in our fenland, but do not! 



Cambridgeshire now possesses twenty-two of the twenty-eight 

 species of Potamoyeton listed in the last edition of the London 

 Catalogue, but one of them, P. alpinus, needs confirmation by actual 

 specimens. Prof. Babington had none in his herbarium, nor could 

 he find any among the older collections in the University Herbarium. 

 Burwell Fen has been repeatedly searched for alpinus without success : 

 was a rufous form of P. colomtus, which grows there, mistaken for it ? 



The discovery of P. trichoides in a drain which I had repeatedly 

 searched for years, and where I must have repeatedly seen the 

 species, is another proof of the difficulty of making a complete 

 list of the plants of even a small district. No doubt I had passed 

 it over as a Zannichellia , which genus it much resembles in appear- 

 ance when growing amongst other plants. At the first glance I 

 thought that it was Z. imlustris, which swarms in the fen ditches 

 and drains, but thought it just worth a closer examination ; fol- 

 lowing up the clue thus obtained, I found every plant of the kind 

 I had passed by for about a hundred yards was P. trichoides ! I 

 mention this because it may assist botanists to find the species in 

 other localities in the fens. 



As far as I have been able to observe, the plant is not strictly 

 monogynous (see Crepin, La Flore Beige Etudiee jmr Fragments, 

 fasc. 4, pp. 47-8), but only a single fruit seems to be perfected. 

 Although the stem and foliage are slender and delicate, the plant 

 in deep water attains a length of 6-8 ft. The lower part of the 

 stem is certainly compressed, the upper part almost terete, two 

 branches are frequently produced in the axils of the leaves, and late 

 in the autumn very numerous axillary winter buds are formed, by 

 which the plant is more frequently propagated than by seeds. 

 Owing to the "roading" of the drain, I have not been able to 

 obtain perfect fruit, but the immature examples are sharply keeled 

 with the keel regularly tubercled, so as to appear crenulate in the 

 more immature examples. Mr. Bennett, to whom I sent the first- 

 formed fruit, concurs with me in the identification of the species. 



MYCOLOGIC FLORA OF KEW GARDENS.* . 



The area of the Royal Gardens is a little more than 250 acres. 

 If some adjacent pieces of Royal property are thrown in, the total is 

 some 300 acres, or nearly half a square mile. Taken with the Old 

 Deer Park to the south, the whole space is singularly isolated, 

 bounded as it is on three sides by the bend of the river sweeping 



• From the Bulletin of Miscellaneous Information for April [August], 1897, 

 where a full list of the species is given by Mr. George Massee. 



