lo July, 1909.] A Fuugiis-likc Appeataiice on Apple Trees. 



435 



A FUNGUS-LIKE APPEARAXCE ON IMPORTED AND 

 EXPORTED APPLE TREES. 



D. McAlphic, Vegetable PatJiolognt. 



In a consignment of >oung apple trees, chiefly consisting of Cox's 

 Orange Pippin, sent to this State from England, both the roots and stems 

 were covered with a loose white powder of mealy appearance which gave 

 the impression of the spores of a fungus and, in fart, they were submitted 

 to me for examination in order to determine the nature of the growth. 

 The trees arrived here on 24th May after a vo\age of a little over six 

 weeks and thev were packed in straw in a tight case without any ventilation. 

 They were inclined to be damp and the white mealy powder covering the 

 surface turned brow^n, as soon as it was freely exposed to the air. On a 

 careful examination of the stems and roots, it was seen that the outgrowths 

 invariablv arose from the numerous breathing-pores scattered all o\-er the 

 surface and which are known as leniuels from their being somewhat lens- 

 shaped in anpearnn"t'. 



iX I-:i'IDERMIS. 



In order to understand the appearance presented by the apple trees, it 

 will be necessar\ to consider the nature of some of the contrivances which 

 exist in plants to allow of the interchange of gases between the exterior 

 and the interior. It is just as necessary for a plant to breathe or respire 

 as it is for an animal, and there are numerous little openings on the surface 

 of leaves, gene.rallv on the under surface where they are more protected, 

 to permit of the aeration of the tissues. If the skin or epidermis be 

 detached from the under surface of a Geranium leaf and examined under 

 the microscope, it is .seen to be studded all over with little openings or 

 breathing-pores known as stomaia, shown in Fig. i. Each opening or 

 stoma is composed of two sausage-shaped cells, facing each other .with 

 their conca^•e sides and attached firmly at either end. The opening between 

 is like a little mouth enclosed by two lips and, although each one is 

 exceedingly minute, they make up for this by being exceedingl\ numerous. 

 In some leaves, there are as manv as 180,000 to the square inch and 

 generally thev are open during the day and shut at night. 



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