1920] 



SMITH— BULBILS OF LYCOPODIUM 



431 



may arise either by branching of preexisting strands, or from the 

 meristem. I have also found that a strand when traced upward 

 may gradually diminish in size and ultimately disappear. In the 

 stem of which figs. 9, 10, and n are sections, the leaves were 9- 

 ranked, and this ranking continues in both the branches, not- 

 withstanding the reduction of protoxylem strands from nine to five. 

 As shown many years ago by Cramer (2) and Hegelmaier (4), 

 there is no relation between the number of orthostichies and the 

 number of xylem strands. The leaf traces of Lycopodium, so far 

 as they have been investigated, are mesarch in structure (7, 8). 

 They are so in L. lucidulum. The trace separates very gradually 



1 



* -- 



12 



Figs. 12-15. — Fig. I2 > tangential section of young bulbil: /, first pair, j, third 

 pair of lateral leaves; fig. 13, radial section of bulbil rather older than fig. 12; 2, 

 first pair of median leaves; 4, first leaves of bulbil proper; X38; fig. 14, longitudinal 

 section of stem tip and young bulbil: 2b, "supporting" leaf; //, leaf trace; bt, bulbil 

 trace; X23; fig. 15, longitudinal section of older bulbil, leaves numbered in order 

 of appearance; r, root tip; Xio. 



from the protoxylem of the central cylinder, traverses the peri- 

 cycle for a short distance, and then pierces the endodermis, after 

 first pushing it out into the form of a little pocket (figs. 10, n). 

 The separation of the leaf trace causes no gap or disturbance in 

 the central cylinder. Immediately above and below the point of 

 exit the sheath closes. The leaf trace at first consists only of 

 spiral tracheids, but later is surrounded by deeply staining cells, 

 presumably phloem. 



The vascular strand of the bulbil does not at all resemble that 

 of a branch. It is a single strand, similar in every way to a leaf 



