Fungi, Bacteria und Pathologie. 1 1 7 



Various diseases oi quite diiferent aspect are caused upon the citrous 

 fruits and trees by a Single fungus. This fungus is Colletotrichum gloe- 

 osporioides Penzig. The iirst record of the trouble in Florida was in 

 1886, when the fungus was recorded as occurring there. The disease is 

 distributed through most oi Florida, the West Indies, South 

 America,, Australia,, and Malta, and is probably present wherever 

 the orange is grown. All sizes ot trees are attacked. The attack may 

 take place on the fruit, leaves, flowers, and twigs. All varieties and 

 species of citrous fruits cultivated in Florida are attacked. The disease 

 is especially bad on the lemon. This is the result of the niethod of 

 handling preparatory to shipping to market. They are picked green and 

 then placed in „coloring houses" where they are kept warm, and the 

 resultingmoisture creates ideal conditions forthegermination of the sporesof 

 the fungus. The spots caused by the fungus do not show until afterthe fruit is 

 shipped but by the time it arrives in market the spots show, thus cau- 

 sing much loss. The fungus fruits readily under moist conditions. The 

 Spotting of lemons may be greatly reduced by spraying with fungicides. 

 Bordeaux mixture adheres very tenaciously so that it is not as good to use 

 as some of the others. Pruning, cultivation and fertilization to cause 

 rapid growth, and fertilizing with Compounds containing heavy percen- 

 tages of potash are the preventive measures recommended. 



Perley Spaulding. 



Salmon, EäRNEST S v Cultural Experiments with „Bio- 

 logie Forms" oi the Erysiphaceae. (Philosophical Trans- 

 actions of the Royal Society of London. Series B. Vol. 197. 

 p. 107—122.) 



The author's abstract is as follows: 



In the introduetory remarks the author points out that through the 

 specialisation of parasitism „biologic forms" have been evolved in the 

 Erysiphaceae which, both in their conidial (asexual) stage, and ascigerous 

 (sexual) stage, show specialised and restricted powers of infection. The 

 powers of infection, characteristic of each „biologic form", are under 

 normal conditions sharply defined and fixed, and hitherto the result of 

 the experiments of numerous investigators — both in regard to the pre- 

 sent group of fungi and to the Uredineae, where the same specialisation 

 of parasitism oecurs — has been the aecumulation of evidence tending 

 to emphasise the immutability of „biologic forms". 



The second part of the paper gives the results of cultural expe- 

 riments with „biologic forms" of Eryslphe gramltils DC. carried out 

 during the past summer in the Cambridge University Botanical Laboratory. 

 It has been found that under certain methods of eulture, in 

 which the vitality of the host plant is interfered with, 

 the restricted powers of infection, characteristic of 

 „biologic forms" break down. 



In the first method of eulture adopted, the leaf, which was either 

 attached to a growing plant, or removed and placed in a damp Chamber, 

 was injured by the removal of a minute piece of leaf-tissue. In this 

 Operation the epidermal cells on one surface, and all or most of the 

 mesophyll tissue, were removed at the cut place, but the epidermal cells 

 on the surface opposite the cut were left uninjured. Conidia were sown 

 on the othercuticular surface of the uninjured epidermal cells over the cut. 

 In a few experiments the conidia were sown on the internal tissues of 

 the leaf exposed by the cut, and these gave the same results. 



Using this method of eulture, over fifty successful experiments, of 

 which details are given, were made. In these the conidia of certain 

 „biologic forms" were induced to infect „cut" leaves of host species 

 which are normally immune from their attacks. 



The experiments proved that the ränge of infection of a „biologic 

 form" becomes increased when the vitality of a leaf is affected by injury, 



