502 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the making of species or even varieties on unstable characters, such as 

 colour, odour, taste, etc. A criticism is also given of the paper on 

 Russida by F. Bataille, from whom he differs considerably in his con- 

 ceptions of species, etc. 



Ambrosia-Fungus. — While investigating cases of gummosis in 

 young and old trees of Acacia decurrens at Amani in East Africa, 

 A. Zimmerman* found that channels had been bored in the branches 

 by beetles belonging to those known as Ambrosia-beetles (Xyleborus). 

 Exudations of gum were found at the openings of these channels, and 

 on closer investigation a fungus was frequently found growing in them. 

 This was finally identified with the Ambrosia-fungus which is used by 

 the beetles as food for the larvse. Zimmerman found that the fungus 

 does considerable harm to the trees, as having once gained entrance, it 

 pierces the woody tissues and destroys them. The author gives a full 

 account of the gum formation, and of the injury caused to the tree. 



F. W. Neger \ has studied the galls of Asphondylia, a genus of 

 Cecidomyia insects that form galls on various plants. The interior of 

 the galls has been found to be coated with a fungus similar in develop- 

 ment to the Ambrosia-fungus. Neger had already proved that the 

 Ambrosia-fungus of the wood-beetle was one of the Sphaariaceaa 

 (Ceratostomella) ; he now finds that the fungus of Asphondylia galls 

 belongs to the genus Macrophoma, one of the Sphteropsideaa. Neger 

 gives a list of the plants on which these galls have been found. It has 

 not been proved that all of them contain the fungus, though a great 

 number certainly do. The fungus does no harm to the gall, and is 

 necessary, or at least very advantageous, to the nourishment of the 

 larva. Neger found on the empty galls pycnidia of a Macrophoma 

 which grew on no other part of the plant. Probably the mother places 

 the fungus along with the egg, and the former grows readily in the gall 

 structure — it forms haustoria, by which it pierces the plant-tissues. 



Fungus Diseases of Scale Insects and White Fly. — R. H. Eolffs 

 and H. S. Fawcett % recommend the inoculation of insects by fungi as 

 an aid in checking their ravages. In Florida, where the experiment 

 was tried, the climatic conditions are favourable to fungus growth, 

 and it was found sufficient for infection purposes to tie sticks bearing 

 the fungi in contact with the twig infected with the insects. The 

 spores are washed about over the surface of the plant, and gain entrance 

 to the insects. There are several different fungi that attack these 

 insects, and destroy them without affecting the plants. The paper 

 is illustrated by photographs and drawings of the fungi in different 

 stages of development. 



A paper § dealing with the same subject has been published by 

 Howard S. Fawcett. In connection with work on Citrus diseases he 

 studied the fungi that were parasitic on the scale insect, Alcyrodes Citri. 

 He determined six different kinds of fungi on the insect itself, some of 



* Centralbl. Bakt., xx. (1908) pp. 716-25 (7 figs.). 



t Ber. Deutsch. Bot. Gesell., xxvia (1909) pp. 735-54 (1 pi. and 2 figs.). 



§ Florida Agric. Exp. Stat. Bull., xciv. (190S) 17 pp. (21 figs.). 



X State Univ. Florida, 1908, 41 pp. (7 pis. and 19 figs.). 



