June, 1919] DicJiotomous Branching in Vernonia 489 



A very few plants were found with fasciated stems. Fascia- 

 tion was exceedingly -rare when compared with the dichotomous 

 branching. One shoot was found which was both fasciated and 

 dichotomously branched and which also had a number of twin 

 and forked leaves. The forked leaves have dichotomous midribs. 



At Emporia, Kansas, 24 plants were found with dichotomous 

 stems in a narrow strip through a pasture about one-half mile 

 long. Near Meriden, Kansas, north of Topeka, 55 plants with 

 the dichotomous shoots were found, as the result of a short 

 search in two pastures. Some of these were also twice forked. 



These three stations are about 90 miles apart each way and 

 it is evident that the dichotomous sporting is not local but 

 probably is a characteristic of the entire species, occurring reg- 

 ularly in a given percentage of individuals. From the fact 

 that more commonly only a single shoot among a half dozen or 

 so, which develop on a fair sized individual, is dichotomous, it 

 appears probable that in some years an individual might have 

 forked shoots and in others not. This might easily be observed 

 in transplanted individuals. 



Dichotomous systems are extensively developed in the 

 thallophytes, as in the red and brown algee and also in the 

 gametophytes of the Bryophyta. Among sporophytes of the 

 higher plants the monopodial system of branching or some 

 modification of it, namely, a true lateral branching system, is 

 almost universal, except in the Lepidophyta where a remarkable 

 dichotomous system was developed, as represented in Lycopods 

 and SeJaginellas. In the great tree forms of Lepidodendron and 

 Sigillaria the repeated dichotomy of the crown and of the root 

 system forms a truly remarkable type of tree when compared 

 with our present trees with monopodial or sympodial systems. 



Now it appears exceedingly interesting to the writer that 

 such a dichotomous system should be developed in the ironweed 

 which we may assume has had its monopodial character for 

 millions of years and must have had a purely monopodial 

 ancestry from the beginning of a branching system in the 

 sporophyte. It is a dichotomous factor added in the presence 

 of a monopodial factor of stem development. In the case of the 

 Lepidophyta, the dichotomy was probably originated in a plant 

 without any branching ability whatever in the stem. The 

 Lepidophyta are far isolated in many characters from all other 

 vascular plants. 



