CXXvi PROCEEDI^^GS OF THE ROYAL HORTICULTURAL SOCIETY. 



by this Pondweed. Cutting it down with a scythe, as often practised, 

 only tends to propagate it still more. Monsieur Correvon observed that 

 the only method, as adopted in Geneva, to keep the Water Thyme, 

 Elodea canadensis, in check, was to clear out the pond once in three 

 years. Other members suggested the introduction of water snails, 

 especially Lymncea stagnalis, and species of Planorhis. 



Dendrohium Dimerous. — Mr. E. Young, of Liverpool, sent a flower 

 having only two petals and two sepals, a not uncommon form. 



British OrcKids. — Mr. Bowles sent specimens of Liparis Loeselii, as 

 well as both w^hite and pale varieties of Orchis lat if olia \a,v. incarnata, 

 from Horning, Wroxham. The former is interesting, as showing the com- 

 mencement of the inversion of the lip in Orchids generally. This petal 

 is in Liparis at first erect and posterior, but then lies fiat, so that an 

 insect readily stands upon it. In Ophrijs the lip becomes pseudo-anterior 

 by the flower simply bending over to the opposite side of the plant. In 

 other Orchids the false anterior position is due to a twist of the pedicel, 

 as in Listera, or else of the inferior ovary, as in Orchis. Mr. Bowles 

 observed that the " Liparis is still plentiful at Horning, but owing to its 

 dwarf stature, and the boggy nature of the ground in which it grows, it 

 is easily overlooked. It thrives wonderfully well in an artificial bog made 

 of jadoo in my rock garden. The white form of 0. iatifolia is very 

 abundant, large patches sometimes occurring. Listera ovata (Twayblade) 

 and Ophioglossum culgatmi also occur in a ' dancing bog,' and grow very 

 large. I also send an albino Pedicularis jyahistris." 



Tomatos attacked by fungus. — Mr. G. E. Day sent specimens diseased 

 with Macrosporium Tomato. It was in the young state. The best 

 remedy is spraying with Bordeaux mixture in an early stage of growth. 



Parasitic Disease. — Touching the note on this subject on p. 197, 

 ^Ir. Sharpe, of Westbury, writes : — "It is very helpful to have so great 

 an authority as Dr. Sorauer. Parasites we have in abundance, and useful 

 recipes for combating them. But, speaking from experience, one ventures 

 to emphasize the importance of fortifying our plants against disease. 

 Several years' battle with Tomato Cladosporium led me to this conclusion, 

 which was subsequently strengthened by reading of ^Phagocytosis.' 

 When Cladosporium first made its appearance with me, the posting of 

 aft'ected leaves to various gardening papers brought no help. No help is 

 sometimes good : one is compelled to try to find answers for oneself to 

 such questions as, What conditions favour the parasite ? and, What the 

 host ? And the outcome is an endeavour towards providing ideal climatic 

 conditions for the host, wdth results thus far certainly good, but 

 immunity not absolutely secured. Physiology, observation, and thought 

 have proved useful, and after several years of an ever-increasing tendency 

 to immunity the plants have freedom now, by means of free ventilation 

 and plenty of phosphates and lime." 



Asplenium Tricliomanes, var. — Mr. C. T. Druery shov/ed a plant of this 

 Fern which had several fronds partially bipinnate. It was found in 

 Wales. It was interesting as exemplifying an attempt of a normally 

 pinnate species to assume the form of an exotic one. The variety so far 

 did not approach the incised section, which varies on quite different lines. 



Papaver Bhosas, var. — Mr. C. T. Druery also showed flowers of a 



