50 MINNESOTA BOTANICAL STUDIES. 



phuric acid. This caused a decided swelling of the spiral 

 bands and indicated them to be lignified. 



A superficial observation of these elaiers would probably 

 give one no idea of any law governing their mode of branch- 

 ing. The budding has the appearance of taking place indis- 

 criminately from the ends or from the middle portion of the 

 cell. But a more careful study shows that there is a distinc- 

 tion between the two ends, that one is bifurcated, the other 

 simple. What appears then to be a branch occurring on the 

 intermediate portion becomes a simple case of dichotomous 

 branching from the end, with one member more vigorously 

 developed than the other. In one instance only {PI. IV. tig. 9) 

 an elater was observed in which both ends were bifurcate. 



This distal branching of the elaters may be explained as be- 

 ing due to their radial arrangement within the sporogonium. 

 They grow upwards from the base in all directions. This 

 causes the two ends to develop under different conditions, and 

 hence they come to be different in character and in capability. 

 The basal ends are crowded and pressed together, and there- 

 fore become attenuated, while the apper ends, from the shape 

 of their enclosure, have more than enough room in which to 

 grow, and as a result they first assume a truncate form and 

 then, subsequent to the loosening up of the contents of the 

 sporogonium, they begin putting forth buds to fill up the unoc- 

 cupied space. This fact was shown conclusively in the case of 

 the sporogonium mentioned above, which, though the youngest 

 one examined, could not be said to be in an early stage of devel- 

 opment. Yet in this entire mount there were not more than 

 six or seven branched elaters, and in these the protuberances 

 were very rudimentary, as shown in the figures. Some recep- 

 tacles did not contain a single branched elater, and often some 

 of the sporogonia in a receptacle would furnish branched 

 elaters while others would not. 



As a further instance of this tendency to branch at the upper 

 ends, it may be noted that SuUivant** speaks of the upper ends 

 of the elaters of Lejeunia as being truncate-dilated. 



This phenomenon, then, is but another example of the incli- 

 nation of cells to enter upon a new period of growth, under 

 conditions of relief from pressure, or in other words, of their 

 tendency to fill space. The analogy is thus apparent between 

 the branching of elater cells and (1 ) the budding of the Yeast 

 plant and of VaucTieria or Botryclium, (2) the formation of armed 



44 SuUivant, Gray's Manual, Ed. I. 685. 1S48. 



