380 



JOURNAL Ub' THE KOYAL JlOUTJ C'U LTU I{A1j SOCIETY. 



Parasites on Leaves, Effect of. By h]. S. Keynolds {Bol. Gaz. 



pp. o65-31)5, May lUJ'J; 9 figs.).— Twelve species iiiiacked by vafioiis 

 fungi were examined and the cytology carefully investigated. Tlie 

 author found evidence of abnormal division of the nucleus. Tlie 

 composition of the cell-wall of the leaf is also altered, being browned 

 possibly by the deposit of tannin. The chloroplasts are sometimes the 

 first to disappear. When leaves are attacked by rust, there is hyper- 

 trophy, enlargement of the nucleus, and increase of protoplasm. 



Sometimes tlie nuclei vanish or an unusual activity of nuclear 

 division set in. The first reaction is sometimes the formation of a 

 granular protoplasm. In one case the rust fungus, which was para- 

 sitized with Darliica, could not apparently act so vigorously on the leaf- 

 cells, giving the host time to react to its influence. 



The mode of attack seems to be through the aid of some substance 

 injurious or stimulative to the host-cells. The host may produce a 

 defensive toxin. — G. F. S. E. 



Parasitism, Analysis of. By D. T. MacDougal {Bot. Gax. 

 pp. 249-260, OctriDll; G figs.).— The author found that the Gissus sp. 

 was able to maintain itself when artificially grafted on Opuniia' 

 Blakeana and sometimes on Ecliinocaclus, but soon perished on the 

 Tree Cactus, Carnegiea. This last exudes an acrid fluid from fresh 

 wounds, which are soon closed by heavy cork layers. Gpuntia versi- 

 color was able to maintain itself on Carnegiea. The expressed juices 

 of these plants showed osmotic pressures of eleven atmospheres for 

 Gissus, nine atmospheres Opmitia Blal<eana, six atmospheres E china- 

 cactus, seven atmospheres Garnegiea, and 12 atmospheres for Gpuntia 

 versicolor. 



These experiments show that the direct proportions of mineral 

 salts in the sap and its acid-contents have no direct bearing on possible 

 parasitism. 



Attempts to make beans parasitic on the joints of Prickly Pear 

 were not successful, but four species of Gpuntia and Agave americana 

 lived two years when attached to Carnegiea. An Gpuntia discovered 

 living on ParMnsonia was taken off and planted. It made three new 

 joints each from three to four times the bulk of the single joint formed 

 yearly in the previous seven or eight years, and the spines lost their 

 atrophied character. 



Not far short of half of the living species of seed-plants use com- 

 plex food material derived from other organisms by mycorrhizal or 

 parasitic arrangements. The assumption of a mutualistic or depen- 

 dent role is inevitably followed by reductions or atrophies. 



Nothing as yet suggests a possible abandonment of the parasitic 

 habit amongst plants. But in the animal kingdom the palaeozorc 

 ancestors of the Limpet appear to have been largely parasitic on the 

 crinoids, but are not now parasitic. — C7. F. S. E, 



Peach and Citron Pest, A (Prosayleus phytolymus) [Agr. 

 Gaz. N.S.W. vol. xxui., pt. iii., pp. 262, 263; 1 phte). —ProsayleKfi 



