OF BaCCIIAKIS C.KMSTI-.l.I.OIDES <»{)'•; 



tropic reaction. The stem had turned towards the li^ht, the bend- 

 ing region extending to about 3 cm. from the tip. The two wings 

 nearest the aperture had turned at right angles to each other and 

 in the direction of the rays, the third wing had moved to a po.sition 

 just behind and parallel to one of the others. In this way only its 

 very edge was illuminated. Although at first it seemed as if the 

 wings must have played a positive part in the movement towards 

 the light, probably a purely mechanical explanation is to be as- 

 signed for their position. By experiment it was found that these 

 would be the positions assumed by any rigid objects — such as 

 strips of cardboard — fastened to a bending axis, so that probably 

 only the .stem was directly concerned in the reaction. 



TuF. Leaf 

 The leaves themselves vary in size. The largest found measured 

 2.2 X 1.3 cm., the smallest 5x3 mm. (f.j). They appear, as 

 above pointed out, at the basal portion, but also occasionally on 

 new shoots, developing from buds on these regions. A transverse 

 section of the leaf (/. 10) shows that here also we have a fairly 

 compact mesophyl structure. The intercellular spaces are, as in 

 the wings, comparatively small. In the leaf, however, sharply 

 distinguishing it from the wings in structure, we find a noticeable 

 dor.si-ventral differentiation ; for not only has the leaf a definite 

 palisade parenchyma of two layers of cells, but a difference is also 

 to be observed in the number of stomata present on the two sur- 

 faces. There are 106 stomata to the square millimeter on the 

 lower surface to 50 on the upper. It is to be noted as significant 

 that the whole number of stomata per square millimeter would aver- 

 age almost exactly the same in the case of the wing and the leaf. 



Reversion to the Juvenile Leaf-form 

 Several experiments were started with a view to inducing the 

 re-formation on adult shoots of the juvenile leaf-form. Some of 

 the growing shoots were kept in a moist chamber, others in a dry 

 and still others in a dark chamber for several weeks, but no results 

 were obtained. This may have been due to one or more of several 

 causes. First, of course, these particular agents may not induce 

 leaf-formation in this plant ; or again the failure may have been 



