174 



from the effect of cine iodid of chlorid, the elements of the schlerenchyma 

 cushions, which were formed later, turn blue after some time, either 

 throughout or in the innermost lamellae of the walls. 



The growth of these schlerenchyma cushions takes place in a meriste- 

 matic layer (w?) formed underneath the dead bark and appears at first as if 

 it would develop into a flat cork layer, cutting off the centre of the diseased 

 tissue, as may be observed in the Fiisicladium cushions. This, however, is 

 not the case. The meristematic layer is active as long as the fruit is green 

 and growing. Toward the periphery it forms new thin-walled bark cells 

 (usually in small numbers) which again are gradually attacked by bacteria 

 and fungi, while on its inner side, toward the (usually seedless) core, the 

 thick-walled elements of the stone cell cushions are increased. 



The radial arrangement of the cell rows in these is explained by the 

 tension of the tissues which the swelling of the unripe fruit causes. If, in 

 this, the new formation of stone cells is greater than the distension of the 

 parenchymatous tissue of the fruit flesh, the stone cells are pushed out like 

 cushions. As a rule, however, both processes keep step and finally, by the 

 death of the pathogenic meristem itself and the breaking of the connection 

 between the outermost stone cells, is produced the crumbly constitution of 

 the stone spots. 



It is a matter of course that fruit attacked by Lithiasis is unfit for 

 consumption. 



Since this phenomenon is not found in all varieties, and not every year 

 even in the same varieties, but is a destructive factor only on dry soil in dn' 

 years, the supposition, that the stock used in grafting influences the problem, 

 seems probable. Weakly growing stock which cannot take up sufficient 

 amounts of water from a dry soil for a rapidly growing top, because of its 

 small root area, will favor this stony condition. If, on this account, the dis- 

 ease should occur repeatedly in the case of dwarf trees on light ground, an 

 attempt should be made to graft pears on the most rapidly growing varieties 

 of quince. When standard trees are in question, an attempt to overcome the 

 difficulty should be made by renewing the soil, fertilizing the sub-soil and 

 watering abundantly ; in obstinate cases, by means of renewal of the top by 

 pruning after fertilization. Some method of forcing the fruit to swell as 

 rapidly as possible might best protect it from an excessive formation of 

 stone cells. 



Varieties of Fruit .Suitable for Dry .Soils. 



The guiding idea of our manual is that many diseases of cultivated 

 plants may be prevented by a more careful consideration of the relation 

 between the character and habits of the plant and its environment. In 

 accordance with this plan in treating diseases favored by drought, w^e men- 

 tion a number of w^ell-known varieties suitable for dry soils^. 



1 Oberdieck, Deut.schland.s be.ste Olistsorten. Leipzig-, VoiRt. ISSl. L. indicates 

 that the variety is recommended to the agriculturist. Str. suitable for planting 

 along streets. The name of the month aftei' that of the variety indicates the time of 

 complete ripening. 



