3] 



PHYSIOLOGICAL REACTIONS 



91 



^^r\- 



D E 



Fig. 23. — Modifications for storing food or catching insects. A, expanded 

 storage-root of Turnip (Brassica campestris) ( i); B, Ginger {Zingiber) plant 

 with enlarged storage rhizomes ( X I); C, bulbs of Lily {Lilium sp., left) and Onion 

 {Allium cepa, right) (X f); D, Sarracenia, a Pitcher-plant, showing flowers and 

 pitcher leaves (x \); E, Sundew {Drosero), a carnivorous plant (x i). 



and ' fixed ' through long evolutionary history. ^ Of such a deep- 

 seated and lasting nature are most of the vegetative and reproductive 

 features which go to make up a plant species, gi^■ing it its special 

 form or morphology. By this we classify it as part of a systematic 

 hierarchy in the manner explained at the beginning of Chapter II. 



^ Often the same character-manifestation is hereditary in one group of plants 

 and due to direct environmental impress in another — an example of the latter 

 being the compact form of many alpine plants as opposed to those characteristic 

 of deserts. In such instances special cultivation may be necessary to determine 

 to which category a feature belongs. 



