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PRINCIPLES OF PLANT- TERATOLOGY. 



. The varieties conglomerata and minima of the ivy 

 (Hedera Helix) produce, instead of the dorsiventral 

 creeping shoots, erect ones of radial symmetry, with 

 distichous phyllotaxis. 



The rliizophores of Selaginella, in their abnormal 

 condition, are very striking examples of this phe- 

 nomenon. From the almost vertically descending they 

 change to the vertically ascending or erect direction 

 (Plate VIII). 



3. Inverted Shoots. — A hyacinth-bulb, owing to 

 injury at the base, produced adventitious bulbous 

 shoots which grew vertically downwards in one and 

 the same line as the normal shoot at the other end. 

 To grow thus was doubtless the best plan they could 

 adopt in order to obtain the necessary light and air. 

 The bulb was growing in a vase of water. 



A good example of this is afforded by the "weeping" 

 varieties of trees, such as the elm and birch, in which 

 the branches, or their terminal portions, are directed 

 vertically downwards. This is the normal feature in 

 the case of the rhizophore of Selaginella (which has 

 here been shown to be a shoot), and in that of the early 

 stages of the growth of certain rhizomes and runners 

 which at first grow vertically down into the soil before 

 assuming their usual horizontal or oblique direction 

 of growth. 



4. Winding Shoots. — The winding of fasciated shoots 

 has already been mentioned ; it is often wrongly called 

 " contortion." Other cases, in which the shoot similarly 

 departs from the vertical direction, are afforded by the 

 flexuous, tortuous shoots of the rush (Juncus), varieties 

 of the hawthorn (Crataegus), and others. It occurs also 

 in herbaceous plants, e. g. chicory and snapdragon. 



Conclusions. — The majority of the phenomena 

 coming under this heading are progressive, and not 

 reversionary ; they represent new departures in the 

 life-history, as in the case of " weeping " and fastigiate 

 varieties of trees. 



There are two cases mentioned which are, however, 



