THE ANATOMY AND AFFINITY OF DEPARIA MOORE1, HOOK. 847 



lvi, lv). Its xylem soon divides into two groups, but its endodermis shows little or 

 no sign of dividing (text-fig. liv). The right adaxial strand has meantime sent out 

 a projection of its xylem towards the abaxial bundle, and the endoderma of those two 

 come together and unite (fig. 3, and text-figs, liv, liii). This is, however, only a 

 local junction, and at a slightly higher level the bundles are again separated and the 

 projection of xylem in the right adaxial strand is nipped off from the main xylem 

 mass as a little group of tracheides (text-fig. Hi). Still higher up the elongated 

 abaxial bundle divides into two small circular strands. The left-hand bundle of the 

 two thus formed now approaches the left adaxial strand (text-figs, li, 1), and when 

 they have partially united by the union of their endoderma the condition repre- 

 sented in fig. 2 and text-fig. xlix is arrived at. A local separation of the small 

 strand already partially distinct from the right adaxial bundle may occur (text-fig. 

 xlviii), but the union thus severed is at a slightly higher level restored (text-fig. 

 xlvii). In the immediately succeeding region the adaxial strands are elongated, and 

 the xylem of the left-hand one is divided (text-fig. xlvi). The division of this 

 original adaxial strand is next accomplished while the right adaxial strand is pre- 

 paring to undergo a similar division into two, and the small bundle loosely associated 

 with it has finally become separated from it (text-fig. xlv). When at a slightly 

 higher level the division of the right adaxial strand has taken place, and the minute 

 bundle on the extreme left is free from its larger associate, the trace consists of four 

 large and three small strands, seven in all (text-fig. xliv). Of these, two large and 

 one small are already grouped in a middle position as the vascular supply to the 

 middle pinna. The separation of the three pinnae from each other, and the 

 establishment in each of a trace of three strands is illustrated in text-figs, xliii, xlii. 

 This separation into nine strands — three of which supply each free pinna — is not of 

 course accomplished by the simultaneous division of the adaxial bundles in the 

 traces of the lateral pinnae, but is in accordance with the levels at which those 

 pinnae depart. 



It will be evident that the following steps in this process are fundamental : the 

 division into two of the original small abaxial strand from the top of the rachis ; the 

 association of one of those thus formed with one of the large adaxial strands ; the 

 separation of a small abaxial bundle from the other adaxial strand ; the division of 

 each adaxial strand into two bundles of fairly equal size ; the central grouping of the 

 three strands of the middle pinna ; and the further division into two of the remain- 

 ing single adaxial strands, which, with their small abaxial associates, enter the 

 lateral pinnae. 



The other details are peculiar to the particular leaf investigated. The details of 

 the pinna-traces as they ascend into the lamina are naturally variable, but because 

 the underlying plan in all three pinnae was found to be the same, the trace of a 

 middle pinna alone will be briefly outlined. 



It is roughly illustrated in the series of figures (text-figs, xli-xxvii, and fig. I). 



