212 BOTANICAL GAZETTE [September 



leaf as pseudo-girdling, whose cause is to be sought in the accident 

 of its development. When the inner face of a leaf encloses a mass 

 whose diameter is less than 3 mm (fourth leaf in fig. 12), the vascular 

 bundles of that leaf are all vertical; but when the enclosed mass, by 

 its enormous radial growth, has reached a diameter of 5-8 mm and 

 comprises two or more developing leaves (second leaf in fig. 12) the 

 base of the enclosing leaf enlarges its inner face accordingly. The first 

 stage in the enlargement consists in an increase in the number of 

 cells, but the second in a horizontal elongation of these {text fig. 1). 

 While this is going on the older part of the central vascular cylinder 

 is also increasing its diameter, separating farther and farther the 

 original positions of the bundles of the leaf. As a result, the marginal 

 traces gradually elongate as they are drawn more and more from the 

 vertical position, and their upper parts stretch outward in the direction 

 which the leaf takes. These facts have been observed repeatedly; 

 whether they are an adequate solution of the problem of the cause of 

 girdling, as Matte thinks, I am unable to say. 



In seedlings with three or four leaves, the stem bundles (u, fig. ig) 

 branch repeatedly, and many of the branches reunite to form a small 

 number of traces. Each of the remaining ones now forks once, the 

 larger member in each instance going to the leaf as before, the smaller 

 one continuing in the axis. Thus, even at this early stage, there is 

 present the sympodial stem described by Miss Smith (ii) for older 

 plants. 



The number of strands entering successive leaves was seen to 

 increase, sometimes with great regularity. In the plant whose 

 dissection is represented in figs. 11 and 12, the number of traces 

 was increased by one in each successive leaf, from the cotyledon 

 with three, to the fourth leaf with seven ; but the increment was not 

 so constant in all the plants observed. 



Within the leaf base and in the petiole, the bundles branch and 

 anastomose freely. There is no real H in these first leaves; the 

 bundles are arranged simply in an open arch. Text fig. 2 is a study 

 of a foliage leaf which was the second lateral organ of the plumule, 

 that is, it was preceded by only one scale leaf. The scale leaf had 

 four bundles; this leaf has five (a, b) ; but just above the stipules the 

 number is reduced to four by the approximation of two of them (c). 



