24 Alfred J. Eivart: 



found whose centres lie between two vascular bundles instead of on 

 either. 



7'he vascular system of the ajjple. 

 In a paper published by the Linnean Society of New South 

 Wales, vol. xxxvi., 1912, pp. 613-656, D. McAlpine describes 

 the vascular system of the apple (and pear), and apparently con- 

 sidered that its existence was unknown to Sachs and other botanists. 

 As a matter of fact, the vascular systems of the apple and pear, as 

 well as of fruits generally, were first described and figured by 

 Nehemiah Grew in the year 1682 (Anatomy of Plants, Book IV., 

 pp. 179-182, plates 65-67). Grew's description stands to the 

 present day without modification, except that in the words " from 

 which (the main branches) a few small fibres are dispersed without 

 any order through the apple," "few" should be "numerous." 

 Wortmann, in 1892, specially discussed the relation of the fine 

 bundle endings and branches in the pulp to bitter pit, and Brooks 

 (Bull. Torrey Botanical Club, xxxv. p. 423, 1908) represents the 

 vascular system of the apple, and made dissections of the vascular 

 network from frozen pulp. References to the. vascular network in 

 the apple are scattered throughout the literature dealing with the 

 diseases of the apple. Hence it is difficult to understand why 

 McAlpine (Report p. 36), describes the vascular network in the 

 apple pulp as " this wonderful and hitherto unsuspected struc- 

 ture," and when McAlpine states (p. 28), " I venture to think that 

 if these vessels, as well as the wonderful vascular network inune- 

 diately beneath the skin, where the bitter pit originates had been 

 recognised by Professor Ewart, he would have arrived at a very 

 different conclusion," he makes both a misleading and an unwar- 

 ranted statement. 



A curious error also lies in the statement that " the vascular 

 network is a strengthening system or skeleton," "with a fibrous 

 portion to strengthen the delicate cells and prevent collapse." 

 (p. 36). Fortunately for orchardists, this statement is untrue, 

 since were it true apples would be difficult or impossible to eat raw, 

 Cursory examination of the vascular bundles under the microscope 

 shows the feeble thickening of the wood vessels which are conduct- 

 ing rather than skeletal structures, and the conspicuous absence 

 of true skeletal elements such as wood fibres, sclereiichyma, collen- 

 chyma, etc. The rigidity of the apple is due to its distended pulp 

 cells almost entirely, and when these collapse or lose water, the 

 tissue becomes soft and flabby, although the rigidity of the vascular 

 system is unaltered. The latter resembles a capillary blood system, 

 rather than a skeletal framework. 



