

1920] 



SMITH— BULBILS OF LYCOPODIUM 



429 



are small and closely arranged about the growing point (fig. 4). 

 The axis of the bulbil proper develops endogenously two small 

 rootlets, which remain imbedded in the fleshy leaves until the 

 germination of the bulbil, when they push out into the soil. 



Anatomy of stem apex and bulbils 



L. lucidulum has only one mode of branching, namely, by 

 dichotomy of the apex. The growing point of the stem tip is broad 

 and flat, or slightly raised in the center, and is surmounted and 

 protected by the more rapidly lengthening leaves. In Lyco podium 

 there seems to be a relation between the form of the growing 

 point and the rate of growth. Slow growers, such as L. lucidulum 

 and L. Selago, have the apex as described (fig. 6); while rapid 



7 



Figs. 5-8. — Fig. 5, tangential section of bulbil: r x and r 2 , roots; 5, fleshy leaves; 

 X5; fig. 6, apex of stem: sp, young sporangium; X38; fig. 7, beginning of dichotomy 

 of stem in longitudinal section; X38; fig. 8, more advanced stage of same; X23. 



growers, such as L. clavatum, L. annotinum, and L. alopecuroides, 

 have the apex conoid in form and considerably in advance of the 

 youngest leaves. Before the apex branches it becomes wider 

 (there is considerable variation in the width of the growing point 

 without any apparent relation to branching). The initial cells of 

 the middle region now cease to grow and multiply, while those 

 on either side continue their activity (fig. 7). Soon the two grow- 

 ing points, separated by a cleft, begin putting forth leaves on all 

 sides (fig. 8). In longitudinal section it can be seen that the 

 central cylinder has divided into equal strands, and the two apices 

 are similar in all respects. 



