827 



transported in this way is small and, therefore, insufficient for any new- 

 structures worth mentioning. The plastic substances are carried much 

 more poorly organically upward, i. e. toward the tip, than organically 

 downward. 



As we see from cuttings set upsidedown and can perceive also from 

 intentionally reversed grafts, under favorable conditions a transference of 

 all fluid materials in the plants, the raw soil solutions as well as the plastic, 

 organized constructive substances, is possible in all directions. The most 

 easily passable paths are naturally used first; when any hindrance occurs 

 there the side paths become of increased importance. In cuttings callus can 

 be formed on every wounded place and this callus can produce axes con- 

 taining chlorophyll and roots. Whether such a case will actually occur 

 depends on external conditions and the typical developmental law peculiar 

 to each plant, changed only with difficulty. Many plants form adventitious 

 roots from the internode so rapidly that the callus formation on the cut 

 surface has not sufficient time to make any development worth mentioning. 



Contradictions in the results of the various observers are explained by 

 the diversity of the external influences. Thus Stoll^ states that no callus 

 became visible with Pogostemon Patchouli, while Hansen^ observed it. The 

 former found no new vegetative points were developed from the callus 

 tissue, while the latter could prove them, etc. 



In practice it is advisable in propagating bushes not to make cuttings 

 from ripened, old wood but from succulent shoots, which when possible are 

 taken from plants forced in the winter in greenhouses. Under certain con- 

 ditions it is advisable to make cuttings also from plants, which as a rule are 

 propagated from seeds. It is a well known fact that cucumber and melon 

 plants from seed of the previous year make very luxuriant foliage growth 

 but set fruit less abundantly. Old seed with contents poor in water, how- 

 ever, like wilted seed potatoes and the Hke, behaves more favorably since 

 the vegetative activity of the plant appears to be modified. Cuttings from 

 the tips of vigorous shoots of cucumber and melon plants, forced in the hot 

 bed and bearing the first fruit possibly in May, give within a few days and 

 about this time well rooted plants with greater fertility than plants from seed. 



Here, at the end of the chapter, it is necessary to call attention to the 

 fact, that propagation by cuttings is often used for the development of new 

 varieties. Many teratological and pathological conditions, which appear 

 temporary in dififerent parts of the plant, become fixed in the cutting. A 

 great many plants with highly variegated foliage, varieties with double 

 blossoms, etc., which originally appeared on isolated shoots, have been made 

 permanent by cuttings. Temporary juvenile stages in Conifers varying 

 with the place of growth are propagated further by cuttings and offered for 

 sale as new forms or varieties. A few striking examples of this kind form 



1 Tiber die Bildung- des Callus bei Stecklingen. Bot. Zeit. 1874, Nos. 46 and 47. 



2 Hansen, Ad., tJber Adventivbildungen. Sitzung-sber. d. phys.-med. Sozietat 

 zu Erlangen June 14, 1880. 



