Subordinate and Herbaceous Flora 35 



racial organization. They may be combined with any or all of the pre- 

 ceding features of somatic reduction observed in deteriorated arboreal forms. 

 With the loss of the necessity for a rigid axis, mechanically efficient over 

 many years, the cambial mechanism and that particular type of vascular 

 structure may be even wholly lost. In the great majority of cases the 

 herbaceous stem presents only vestigial traces of its former timber-produc- 

 tion. From the rhizome, or lower portion of the plant, retained at the soil- 

 level in safe perennation, annual shoots of photosynthetic value, ultimately 

 flowering and fruiting out, are alone produced ; or the main axis may be 

 reduced by the loss of intercalary extension to a mere basal ' rosette '. 



Somatically the herbaceous plant is in essentials only a greatly reduced 

 and deteriorated version of the original arboreal form from which it came ; 

 but reproductively it has gained enormously in efficiency. A big body is 

 after all of no use in itself except as providing a large supply of food-material 

 on a grand scale. With increased efficiency of floral mechanism, seed- 

 formation, and seed-dispersal to new ground, the wastage-problem may be 

 so successfully compensated that such vast spore and seed-output is no 

 longer requisite. The machine becomes more efficient as more economical. 

 The more a plant is enabled to withstand the disadvantage of a short 

 working-season (following reduction of water-supply, light, or temperature), 

 and the quicker it returns its seed-output, the more highly organized is the 

 racial mechanism, and the higher the type in the scale of organization. 

 Evolution measures races against races, not individuals against individuals. 



So long as the plant can dominate the environment under optimum 

 biological conditions, however short they may be in point of time (season- 

 ally), and endure perennation during an alternating period of stress, the 

 latter is forgotten in the high degree of activity and specialization of the 

 former ; just as an organism which sleeps to live with renewed activity on 

 waking, is regarded as more highly advanced in the scheme of life, than one 

 which never sleeps because it never works at an intensive rate. The intro- 

 duction of an intensive time-factor, as tending to get a move on in evolution, 

 is the thing which greatly counts. 



From this standpoint, the herbaceous perennials of extra-forest zones 

 represent one of the crowning phases of modern vegetation, and phases of 

 somatic reduction may be carried to extremes. Absence of cambial increase, 

 associated with the restriction of stems to annual duration, may end in the 

 suppression of all vascular construction. Want of mechanical tissue again 

 leads to a prostrate or creeping habit, which is further emphasized by change 

 of geotropic response. While omission of intercalary extension may give a 

 rosette-habit, extreme development of this factor, combined with preceding 

 reduction-effects, gives the ' runner ' and ' stolon ' of the rhizomatous habit. 

 On the other hand, the fact that all these factors may be retained in the 

 erected inflorescence and floral axes, shot up as miniature arboreal growths 

 for the function of flowering and fruiting, indicates that their suppression 

 in the herbaceous perennial, with a limiting case in the creeping underground 

 rhizome, is still wholly secondary ; and again implies a very special habit 

 adapted to the needs of a special type of vegetation, rather than being a 

 ' primitive ' condition. 



The special value of the Herbaceous Perennial in the scheme of plant- 

 life, consists in the fact that it can occupy stations available for some part of 

 the year, where large trees cannot maintain existence through the extremes 

 of the seasonal changes. It represents the highly specialized response to 

 extreme seasonal change, with short working-period, when sunlight and 

 water-supply may be at an optimum ; hence in the shortened season of a 

 northern climate, herbaceous representatives of many families compete on 



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