" WOOLLY STRIPE" OF SEED VESSELS, ETC. 



19 



A summary of the occurrence of these filamentous structures in the apple will show how 

 widely distributed they are — 



(a) When an apple is cut across through the core, a white fluffy substance is seen at the 

 sutures or seams where the ripe carpels split, and this consists of colorless, 

 branching, warty, hair-like filaments, composed of cells containing starch. 



(/>) Very often, but not always, on the inner face of the cartilaginous walls of the seed- 

 vessels, there are " woolly stripes," consisting of similar filaments, and arising 

 from ruptures in the lines corresponding to the stripes (Fig. 51). 



(c) When an apple has been struck by hail and the cells of the flesh beneath the skin 



have been ruptured and become brown, there the self-same filaments are to be 

 found ramifying in the tissue. 



(d) When an apple has been bruised artificially or otherwise, so that the pulp cells are 



ruptured, they become brown, and the filaments appear as before. 



(e) When the frost affects an apple, particularly in the early stages of growth, there is 



a zone to which it reaches, and there is a kind of separation of the tissues where 

 the frozen and sound portions meet. In that zone the cells become brown, 

 forming an interrupted circle, and there is a luxuriant development of the filaments. 



(/) In the brown spots of Bitter Pit, the same filaments are to be found where the cells 

 have separated and formed cavities, but much more sparingly than in the former 

 cases. As will afterwards be shown, there is not a bursting of the cells in Bitter 

 Pit, but only collapse, so that the rupture mainly occurs where the cells are 

 already dead, and it is only living cells which are capable of growing and giving 

 rise to the filamentous structures. 



(g) In the cavities formed by " crinkle " the hair-like filaments are also found, and they 

 adjoin the brown cells as in other cases. 



It will be observed that these filaments, composed of rows of delicate cells, only occur wherever 

 there has been an internal rupture, and this rapid multiplication of thin-walled cells is evidently 

 due to the irritation produced by the rupture. First of all we observe that the filamentous rows 

 of cells arise from adjoining uninjured cells of the flesh, and Fig. 53a shows such a cell growing out 

 into a filamentous structure. 



Now, this rapid multiplication of cells is not unusual in plant tissues when they have been 

 stimulated into activity by various agencies, such as insects or fungi, only it has not been specially 

 noticed as arising from an internal rupture. 



When a plant is wounded, it is well known that this acts as a stimulus to the rapid formation 

 of cells, as, when the delicate cells of the cambium are cut with a knife, they respond by 

 covering up the dead cells with a fresh and luxuriant growth. So in the case of an internal rupture 

 or wound, the adjoining cells of the flesh are stimulated into renewed activity, and, instead of 

 enlarging in the normal way, they produced numerous tufts of relatively small, thin-walled cells, 

 assuming the form of a filament from their rapid growth. It has also to be noted that such cells 

 contain starch-grains, which are coloured blue by iodine, and the terminal cell is usually filled with 

 a finely granular protoplasm, resembling the apical growing cell of an ordinary filamentous 

 structure. 



It may be asked what has the development of these abnormal growths to do with Bitter Pit. 

 Well, an ingenious suggestion has been communicated to me by Giissow, that these delicate cells 

 found associated in some instances with the brown spots of Bitter Pit may break down and undergo 

 decay, particularly when the apples are kept in store, and result in the production of brownish 

 spots. The browning of the tissue is not always accompanied by these filamentous structures, and 

 existed before their formation, so that they cannot be the general cause. But it is just possible 



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