GROWTH-FORMS OF FLORA OF NEW YORK AND VICINITY 25 



Helophytes and Hydrophytes. The former has buds at the bottom 

 of the water. They are mostly marsh species such as Typha, Spar- 

 ganium, Acorus, etc. Hydrophytes have perennating rhizomes or 

 winter-buds and are truly aquatic, such as Castalia, Elodea and 

 Potamogeton. 



Therophytes. Annuals. 



A tabular view of these different growth forms, with the abbrevi- 

 ations as used in this paper follows : 



MG = Megaphanerophytes CH = Chamaephytes 

 MS = Mesaphanerophytes H = Hemicryptophytes 



MC = Microphanerophytes G = Geophytes 



N = Nanophanerophytes HH = Helophytes and Hydrophytes 

 T = Therophytes 



Raunkiaer's method of adapting the study of these growth-forms 

 as related to temperature is to estimate the number of species char- 

 acterized by these different forms, and to get the percentages of the 

 different growth-forms in the flora. For the purpose of comparison 

 he established a "normal spectrum" which is constructed on purely 

 hypothetical lines. It consists of 400 species carefully chosen from 

 1,000 representative species. The analysis of these 400 species into 

 their different growth-forms gives, theoretically, the ideal phyto- 

 climatic spectrum of the whole earth. According to Raunkiaer the 

 percentage of species belonging to each growth-form, in the ideal 

 spectrum of 400 species, is as follows: 



Percentage of growth-forms in normal spectrum 4 



Type of growth-form MG & MS MC N CH H G HH T 



Percentage of growth-forms 6 17 20 9 27 3 1 13 



These percentages are supposed to reflect the average condition 

 as to the growth-forms of the whole earth. Of course they may need 

 future revision; it would be strange if they did not as our knowledge 

 of the habits of various species increases. 



The method of comparing the climate of different parts of the 

 earth's surface, on this conception, involves working out the per- 

 centages of the different growth-forms exhibited in the areas and a 



4 I have omitted epiphytes and stem-succulents, as being two of Raunkiaer's 

 groups hardly applicable to our area. 



