214 STUDIES IN PLANT REGENERATION а 
accidentally restored to its original position. In попе of the 
twenty-seven pieces in which the apical end had been marked for 
identification did roots develop. А very slight callus was formed, 
but this soon went over into cork-formation. Normally, then, 
these inverted internodes do not root. 
Experiment 20.-- A similar result was obtained from two in- 
verted internodes of Vitis quadrangularis. Lack of material pre- 
vented further work on this plant. 
Monocotyledonous stem pieces without buds were generally 
found to give negative results even as regards root-formation. 
This may be due to the absence of a cambium to initiate callus- 
formation, but, on the other hand, it is well known that callus may 
originate from almost any parenchymatous tissue. The failure to 
root was probably due to an unfortunate choice of material for 
experimentation. One monocotyledon, however, gave an inter- 
esting result. The “ pseudobulb” of the orchids is morphologic- 
ally a short, thickened stem consisting of one or several internodes, 
in which growth ceases after a single season. In Dendrobium 
Parisii the pseudobulbs usually have four such internodes. 
Experiment 30. — One of these stems two 
years old was placed in sand on November 4, 
1904. Оп February 18, 1905, the presence 
of roots of the aerial type at the base of the 
cutting was discovered, and the part was 
transferred to peat. By October 15, 1905, a 
new shoot had appeared, also at the base. 
The single leaf characteristic of the species 
Eo was plainly visible (Fig. 8). 
96 Because of the well-known difficulty in 
Fic. 8. Pseudobulb of inducing conifers to root,* cuttings were 
Dendrobium Parishii made of seedlings of these plants and of stems 
Mira aul M of plants in their fourth year. 
Experiment 31. — When the entire root 
was removed from seedlings of Pinus Laricio, a callus was formed af- 
ter four weeks at the end of the hypocotyl. From this in seven out 
of the nine cases in which organs were formed, a sin 
gle root, occu- 
*Sorauer, P. Handbuch der Pflanzenkrankheiten, II Auflage 1: 663. Also 
Populäre Pflanzenphysiologie für Gärtner, 169. 189r. 
