SCIENTIFIC COMMITTEE, DECEMBER 11. 



xcv 



leaves by insects, nor did I notice any on the roots. 1 could see no 

 trace of fungi. Is it not possible that the plants had been kept too 

 damp? " 



Cattleya Fly. — Mr. Saunders also reported that " the shoots of the 

 orchids shown by Mr. Bowles were undoubtedly infested by the so-called 

 * Cattleya fly ' (isosoma orchidearum). It is not, however, a Hy, but a 

 hymenopterous insect belonging to the family CJialcididece, the members 

 of which are parasitic on other insects as a rule. The genus Isosoma is 

 placed in the sub-family Eurytomidece, several members of which are 

 found in almost gall-like swellings in the stems and shoots of various 

 plants. I believe that it is still an open question whether these insects 

 are the cause of the swellings, or whether they are parasitic on others 

 which have formed them. This should not be a difficult question to 

 answer if one had sufficient material to work upon, as the parasitic grub 

 ought to be found at some time of its existence devouring the maker of 

 the gall. Considering that the ChalcididecB are nearly allied to the 

 Cyni2miece, who are undoubtedly gall-makers, I am inclined to think that 

 Isosoma is the real cause of the injury to orchids. I cannot recommend 

 any remedy but the very obvious one of burning, or in some other way 

 destroying the infested shoots. The present would appear to be a very 

 good time for doing this, as most of the insects are in the pupal state, 

 just ready to emerge." 



Oncidium Walueiua. Rolfe. — Dr. Masters reported that he had 

 examined this species, referred to him at the last meeting. It was not a 

 new plant, and he could find nothing in its structure to entitle it to a 

 botanical certificate. The committee concurred with this view. The 

 following synonyms and references were quoted : Leiochilus pulcJiellus, 

 Coigneaux, " Fl. Brasil.," orchid x., p. 450, tab. xciv., fig. 11. Walueiva 

 pulchella, Kegel, "Garten-Flora," xL, 1889, f. 1341 ; O'Brien in " Gard. 

 Chron." 1901, xxx. p. 365. 



Boot-formation in Ap^jles. — Mr. Spencer Pickering, F.R.S., showed 

 roots of Apples on Paradise Stock, which had been grown in sand, and 

 were remarkable for the extraordinarily numerous root fibres, some of 

 which were thickened and of a very light colour. He also showed 

 photographs of trees of the same age, and otherwise treated in the same 

 way, but grown in a clay soil, where there was much less development of 

 roots. In those grown in sand, however, the shoots formed were very 

 short, while in those grown in clay they were much more vigorous. In 

 reply to questions he stated that the addition of nutrient salts had had no 

 appreciable effect upon the extent of the root system, nor upon the 

 growth of the branches. The roots were not only of a peculiarly light 

 colour, but were also very soft, the cortical tissue in some being greatly 

 developed ; no investigations as to the number &c. of the root hairs had 

 been made. It was suggested that the structure of the roots was due to 

 the mechanical condition of the soil, and others suggested that the 

 presence or absence of certain species of bacteria that possibly have 

 considerable influence upon the proper action of roots might have caused 

 the remarkable dift'erences noted, but it was clear that much more 

 experiment was needed before a full reason for the observed diflerences 

 could be assigned. 



