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plete loss, giving white. As to time of appearance the change 

 may be permanently uniform for groups of cells or it may develop 

 with age. As to arrangement, the entire leaf may exhibit the 

 change in color, or this may occur only in certain parts, giving 

 patterns such as the striped, the marginal, the centered, the 

 blotched, and the veined or reticulated patterns. 



Perhaps one of the most interesting of variegations is the 

 infectious type — which may be transmitted to plants previously 

 all green. The delicately and finely blotched variegation of the 

 flowering maple (Abutiloji) can be transmitted to certain all- 

 green Abutilons by grafting onto them a branch from a varie- 

 gated plant. The variegation in some species is so infectious 

 that it is easily spread from plant to plant by insects. In 

 tobacco, in potato, and in other crop plants infectious varie- 

 gation or "chlorosis" frequently does much damage. There 

 are many grades or degrees of infectious variegations. In some 

 of these it is thought that certain minute living organisms are 

 present and that their activities are associated with the loss of 

 green. The blotched type of variegation in several of our orna- 

 mentals is known to be infectious. 



Another rather definite type of variegation is that with a 

 white-bordered pattern. If one closely examines a leaf with 

 such a pattern, one observ'es that in addition to the conspicuous 

 white margin about the leaf there is a layer or coating of white 

 over the green both on the under side and on the upper side of 

 the leaf. This is also true of the stem. The plant has a central 

 core of green tissue which is covered by a layer of white tissue. 

 When new leaves develop, the individual cells of the two kinds 

 of tissue multiply and keep their relative positions with remark- 

 able regularity. But occasionally the green tissue breaks through 

 the enveloping white and a purely green branch appears. The 

 reverse may also happen. (Several cases of these so-called bud 

 sports were exhibited.) Many of the striped variegations seen 

 in such plants as the agaves and the grasses are likewise due to 

 the grouping of tissues that are permanently green or white. 

 In this type of variegation there are two kinds of cells, one 

 green, the other with white, or with pale green, and the grouping 

 of these two gives the pattern. 



Aside from the two types of variegation already mentioned, 

 there is a wide range and variety of patterns which appear to 



