372 



into trade which arc said to increase tlie reaction of the soil (for example, 

 snlfarin). 



In connection with scur\ y diseases of edible roots, we would like to 

 call attention also to similar phenomena on smooth barked young trees, 

 which have not as yet been studied. Lindens, elms, oaks, etc., on certain 

 kinds of soil (i. e. moor-soil) had round, rough splits in the bark, which 

 increased greatly in extent adjacent to the adventitious buds or shoots. 

 This bark sciirz'y is frequent near large cities, where the base of the tree is 

 exposed to debris of all kinds. 



Another phenomenon found in barley and wheat, which should be in- 

 cluded in this group, is "spotted necrosis," i. e.. the appearance of deep, 

 dark reddish brown, dying spots at the tip and along the edge of the grain 

 leaves. I^p to the present, T have found the disease most extensively in 

 heavy, clayey, or moor soil, w^hich had had abundant potassium fertilization 

 and also in regions with a deposit of ashes. 



Progressive Metamorphosis. 



While, in tlie cases already discussed in this chapter, we have empha- 

 sized as the common characteristic of all the phenomena, the influence of 

 unsuitable concentrations of the soil solution, because of which tlie i)lant 

 suffers, we will now consider the cases in which the plastic building sub- 

 stances have been increased out of proportion to their utilization. Here. too. 

 an excessive supply of nutrients in the soil does not give rise necessarilv to 

 this condition, but, for various reasons, a disturbance in the equilil)rium in 

 the formative direction of the individual may occur, that is to say, a chamjc 

 in the utilization of the plastic food materials. 



Examples of this are those phenomena grouped under progressive 

 metamorphosis, such as the transformation of leaf organs into a morpho- 

 logically higher developmental form. Teratology classifies such transfor- 

 mations under the heads "petalody'' and "pistillody," i. e., cases in which 

 the calyx bracts become petal-like, or parts of the corolla assume the char- 

 acter of the stamens, or the organs actually belonging to the androe- 

 cium circle are changed into carpels. Numerous examples of ])eta- 

 lody are furnished by the cultivated forms of our Primulae and Ranunculi. 

 We find the best instances of pistillody in the poppy (Papaver somni- 

 ferum). In this plant, as in the different varieties of cabbage, long con- 

 tinued cultivation has so disturbed the morphological rules, that the organs 

 tend to transformation. A most interesting case may be found in the poppy 

 heads which, at the base, bear a circle of many small. Avoody primordia of 

 smaller heads (stamens which have been changed into carpels). In double 

 tuberous Begonias, tulips and other Tiliaceae, specimens are found in which 

 the stamens have been transformed into carpels with seed primordia. Re- 

 lated to this are the phenomena of the "cone malady" in conifers, especially 

 in pines, as illustrated in Fig. 54. 



