8 INTRODUCTION CHAP, n 



5. Size of the plant is of some moment, not only because in the struggle 

 for existence the taller plants are enabled to establish a supremacy more 

 easily, but also because they are more exposed to inclemency of climate ; 

 shrubs reach greater altitudes and latitudes than trees, while dwarf- 

 shrubs and herbs extend even farther than shrubs. 



6. Duration of the leaves varies ; some live for only a few months, 

 others for years. In all climates deciduous (summer-green, rain-green) 

 and evergreen plants are met with side by side. This distinction is 

 associated with edaphic conditions, and can be utilized in the classifica- 

 tion of sub-divisions. 



7. The adaptation of the assimilatory shoot to the conditions of tran- 

 spiration, is determined by the substratum, and by the climate. Some 

 plants assimilate mainly by their leaves, which exhibit very great variety 

 in shape and structure ; but others depute their assimilatory function 

 to the stem, and reduce their leaves. The shapes of leaves (their vena- 

 tion, division, and so forth) depend partly upon systematic affinity, and 

 partly upon the surrounding medium and climate ; they are probably 

 of but slight value as a basis of oecological classification. 



8. The capacity for social life is of great importance in the struggle 

 between species, and consequently in the composition and physiognomy 

 of the plant-community. This capacity is due in some cases to the 

 prolific production of seed, but usually to more vigorous vegetative 

 multiplication by means of travelling shoots, or shoots given off from 

 the root. And this latter is to some extent determined by the soil 

 (moist or wet soil, loose sandy soil, and so forth). 



In accordance with these considerations polycarpic plants may be 

 grouped under four sub-classes : 



(a) Renascent (Redivivus) herbs. 



(b) Rosette-plants. 



(c) Creeping plants. 



(d) Plants with erect long-lived shoots. 1 



We will now proceed to discuss these sub-classes, and, as a final step 

 in the process of sub-division, we shall be able to define types that can 

 be named after definite species or genera, e. g. Primula-type, Bromelia- 

 type, Cycas-type, and so forth. 



(a) Renascent herbs. Polycarpic herbs whose assimilating and 

 flowering shoots develop at a definite climatic time. The plant there- 

 fore passes through a resting period, during which its hypogeous or 

 epigeous renewal-shoots are protected by scale-leaves. When the 

 favourable season arrives, the plant once more reveals itself (and is thus 

 renascent). The photophilous shoots are aestival-annual and usually 

 have long mternodes and mesophilous leaf -structure. The perennating 

 hypogeous parts are necessarily provided with reserve food. 



A great variety of types is included amongst these herbs. Some 

 are spot-bound [stationary, sedentary] ; others are travelling plants. 

 Among them are the following : 



clas .fificatipn approximates to that proposed by Krause (1891). For 

 cES ^ dlV1S10n f these sub-classes, ancf for the distinction of the various 



we must refer to the characters 



