177 



From the beginning one must note that every limited supply of nutri- 

 ment which leads to nanism must express itself mostly in the amount of 

 additional growth, i. e., in the formation of the secondary tissues. An ana- 

 tomical proof of this has been furnished by Gauchery", who cites cases 

 when the cambium has formed anew only a few rows of cells. Often he 

 could no longer determine any meristematic zone whatever between phloem 

 and xylem ; therefore, the original cambium must have passed over at once 

 into permanent tissue as the result of deficient nutrition. 



In the plants which are forced to grow in sandy or stony soil, often 

 with a lack of water, a form of hyperplasia^ (arrested developments) 

 appears. It is not so much the number of the cell elements which seems 

 to be decreased, as their size. Thus specimens are formed which we would 

 like to call "stunted plants." By this is understood woody plants, the growth 

 of which is not retarded to dwarfing but which, by the striking shortening 

 of their axial organs, show a repressed, knarly habit of growth. 



In this habit of growth the very evident, increased spiral twisting of the 

 woody elements of the trunk counts as a typical characteristic. The finest 

 examples are seen in Syringa and Crataegus. We can explain the production 

 of the increased spiral twisting if we think of the direction of the woody 

 cells as the diagonal of the parallelogram of two forces. 



At the apex of each elongating axis there is, on the one hand, an effec- 

 tive striving toward growth in length in which the elongation of the pith 

 body becomes a decisive factor of swelling; on the other hand, the general 

 enlargement of the young cells acts also as the cause of the radial enlarge- 

 ment of the trunk. In considering a very young wood cell in the cambial 

 layer, stretching longitudinally, w^e see that, as the growth in length predomi- 

 nates over the growth in thickness, it is relatively difficult to divert the cell 

 from its longitudinal growth. However, as the abundantly formed young 

 wood cells, during elongation, are pressed outward by the growth in thick- 

 ness of the medullary cylinder in the direction of the radius of the trunk, 

 proportionately just so much the sharper will be their spiral twisting. On 

 this account we find long slender shoots with a slight spiral twisting in 

 plants on moist nutrient soil, and on sandy soils poor in water, or with other 

 checks to growth in length, plants having short axes with strong twistings. 



Confirmation of the hypothesis is found in the "enforced twisting" to 

 be mentioned later. The more the stems are distended like barrels, the 

 sharper is the spiral twisting of the cords of the leaf spur. 



We mention this point because the occurrence of such strongly twisted 

 stunted plants is valuable as a symptom in judging the soil conditions. 



Pilosis. 



Plants grown on dry soil soon have a hairy appearance, even if no more 

 hairs are formed than on specimens of the same variety growing in damp 



6 Gauchery, Recherches sur le nanisme veg-etal. Ann. sc. nat. Bot. 1899. VIII. 

 ser., t. IX. 



1 Kuster, E., Pathologische Pflanzenanatomie, .lena 1903, p. 21. Here abundant 

 bibliographical citations. 



