6 INTRODUCTION chap, ii 



and are connected by the most gradual intermediate stages, also because 

 it is difficult to discover guiding principles that are really natural. Nor 

 is it an easy task to find short and appropriate names for the different 

 types. Genetic relationships, and purely morphological or anatomical 

 characters, such as the venation and shape of leaves, the order of succes- 

 sion of shoots, monopodial and sympodial branching, are of very slight 

 oecological or of no physiognomic significance. Oecological and physio- 

 logical features, particularly the adaptation of the nutritive organs in 

 form, structure, and biology, to climate and substratum or medium, are 

 of paramount importance. Cases, however, are not wanting in which 

 oecological grouping runs parallel with systematic classification. 



Growth-forms may be arranged in the following six main classes, 

 namely : 



1. Heterotrophic. 4. Lichenoid. 



2. Aquatic. 5. Lianoid. -r 



3. Muscoid. 6. All other autonomous land-plants. 



Heterotrophic growth-forms are shown by all holosaprophytes and 

 holoparasites, which are undoubtedly derived from autophytes and are 

 degenerate in form and structure. Hemi-saprophytes and hemi-parasites, 

 on the contrary, are under the dominance of chlorophyll and exhibit 

 the same rich diversity of form as other green plants. (See Chapter XXV.) 



Aquatic growth-forms differ from those shown by land-plants so 

 widely as regards their morphology, anatomy, and physiology, that 

 they must be regarded as constituting a separate class. (See Section IV.) 



The muscoid and liche^ioid growth-forms are seen, almost only, in 

 mosses and lichens. Their powers of enduring extreme loss of water 

 and of rapidly replacing this by means of absorption over the whole 

 free surface, aie oecologically very important. Associated with these 

 characters are a number of others. The distinction between the muscoid 

 and lichenoid types lies in the method of nutrition, as autotrophic and 

 symbiotic respectively. (See Chapter XXV.) 



The lianoid growth-form is mainly determined by social conditions, and 

 shows pecuhar oecological and physiological characters. (See Chapter 

 XXV.) Epiphytes, on the contrary, form an edaphic community of 

 autotrophic land-plants including many different types. 



The sixth class includes the growth-forms adopted by all the remaining 

 autotrophic land-plants that contain chloroph} 11 and, as regards nutrition, 

 are independent of other plants, and are thus autonomous. The growth- 

 forms of Pteridophyta are included here, although these differ so widely 

 from those of Spermophyta as regards their reproductive organs. 



These main classes may, in turn, be divided into sub-classes. In 

 particular, the growth-forms of the autotrophic plants of the sixth class 

 admit of grouping in categories the foundation of which is the duration 

 of the individual plant and of its parts. Upon this basis these plants 

 are divided into monocarpic and polycarpic : 1 the former produce flower 

 and fruit (or spores) once, and then die ; the latter may produce fruit 

 repeatedly before death claims them. 



* In recent times these CandoUean terms have been suppressed often in favour 

 of A. Braun's ' hapaxanthic ' {ana^, once ; avdos, flower) and Kjellman's ' pollakanthic ' 

 {noXkaKis, several times ; avdos, flower). 



