158 



THE AGKICULTURAL NEWS. 



May 6, 1916. 



FUNGUS NOTES. 



LIVE STOCK NOTES. 



MYCORHIZAE. 



The significance of the association of fungus hyphae 

 ■with the roots of plants, in the combinations known as 

 mycorhizae, is of great interest, and is not without bearing on 

 certain cultural and pathological problems arising in tropical 

 agriculture. 



The posiiion of the fungus in the mycorhizal associations 

 allows of their separation into two usually well-marked 

 classes, in one of which the hyphae are mainly external, 

 clothing the rootlets in a weft more or less close, the few 

 which penetrate the root being intercellular: while in the 

 other the hyphae are mainly found inhabiting the cells of the 

 cortex with but few connexions with the exterior. The terms 

 ectotrophic and endotrophic are used to distinguish the two. 



Mycorhizae with the fungus external are very common 

 on temperate forest trees, often causing the suppression, 

 partial or complete, of the root hairs. It has been generally 

 .supposed that the fungus played some part in the nutrition 

 of its host, especially in soil rich in humus, an idea which 

 the general presence of mycorhizae on many forest and heath 

 plants seemed to support. So far as the matter can be tested by 

 experiment, however, little or no evidence has been obtained 

 of any advantage gained by the 'higher' plant. A recent 

 writer* concludes, after an exhaustive investigation, that the 

 ectotrophic mycorhizae of forest trees are not in any sense 

 symbiotic associations, but are instances of parasitism of 

 fungi on the roots of the trees. 



The border line between symbiosis and parasitism is 

 a vague one, and it must be noted that in this case the 

 parasitism is at any rate so nearly approaching symbiosis 

 that in normal circumstances the host cannot be regarded 

 as being to any appreciable extent harmfully atfected 

 by it: the only question being as to whether under any 

 circumstances an actual benefit is obtained. It seems very 

 probable that there exist on different plants gradations from 

 actual harmful parasitism, through toleration, to some degree 

 of symbiosis, so that each case must be considered on its 

 merits. 



In dealing with the endotrophic mycorhizae we are on 

 firmer ground, since it is known that in some cases at least 

 the association is constant and essential to the higher plant. 

 Bernard showed that in the case of some orchids the seeds 

 refuse to germinate until they are infected with tlie fungus, 

 and in others the development of the seedling ceases unless 

 the fungus is present. But what part is played by the fungus 

 in the combination remains obscure. Analogy with the 

 bacterial nodules of leguminous plants has suggested that 

 it is the collection of nitrogen, in exchange for carbohydrates, 

 but there is little experimental basis for the assumption. 

 In well developed cases there is an inward progression 

 from normal hyphae to monstrous forms, with an 

 absorption of the latter by the host, but the origin of the 

 material thus made use of, i.e., whether it comes from the 

 host or from without, is not known. The scanty connexions 

 of the hyphae with the exterior appear to be much more 

 related to entry (often through the root-hairs) than to 

 communication with an external source of food. 



It has recently been shown that in CaUuna (ling), the 

 fungus which is present in the mycorhizae permeates the 

 ■whole plant. 



W.N. 



These notes have been compiled from published state- 

 ments in the Departmental Reports from the different islands, 

 and will be found interesting by all those concerned with the- 

 management of animals in the West Indies. 



Barbados Donkeys. 



The large donkey sire, El Rey, which the Governor-in- 

 Executive Committee presented to the Barbados Agricultural 

 Society, has been stationed at Long Bay Castle during the- 

 year where a number of the large jennie donkeys imported 

 from the United States are kept, and where a number of 

 foals have been borne to him. 



The smaller donkey sire, Don Cavalero, which belongs to 

 a syndicate of planters, has been oil service in various districts 

 of the island. As the foals from this latter animal have got 

 more nuraerous it is difficult to keep an account of them, but 

 it may be stated that they are gradually increasing in 

 number, and soon some of them will be adding to the 

 number of his descendants. In the near future the improve- 

 ment in the breed of these animals should be noticeable. 



Cow.s AND G0AT.S. 



With regard to the twenty pure-bred Holstein cows and 

 bulls, and the seven pure-bred Guernsey cows and bulls which 

 were introduced in 1910 through the auspices of the Bar- 

 bados Department, the same thing applies to these as applied - 

 in the case of the donkeys, viz: that their progeny have 

 become so numerous now that it is impossible to obtain an 

 accurate account of their numbers, etc. 



As has been mentioned in previous reports, owing to 

 the high infant mortality amongst the infants of the peasants, 

 five male goats presented to the Department by various 

 gentlemen were stationed on service about the island 

 for the purpose of improving the breed of the common 

 goats in those districts. 



Live Stock Tkade of St. Vixcext. 



St Vincent has an important live stock export trade with 

 the neighbouring islands, especially with St Lucia. The 

 following table shows the number, kind and value of stock 

 exported during 1914-15, for which the Government i.ssued 

 veterinary certificates, also the colonies to which the animala 

 were exported: — 



*Dougall, W.B. Amerkan Journal Botany I, 51-74. 



Berkshire and Tamworth Boars in the Virgin Islands. 



These boars were imported into Tortola in 1913 with a 

 view to improving the local breed of hogs, and during the- 



