THE STEM OR SHOOT. 



103 



then partaking more of the nature of the 6 ' primordial 

 leaves " borne by the young plant in its early stages 

 of growth than of that of the typical " needles." 

 This interesting phenomenon represents, both as 

 regards the elongation of the shoot and the character 

 and increase in number of its leaves, a reversion to 

 the ancestral condition. Hence it is of extreme 

 interest to compare this abnormality with the case of 

 the fossil plant Prepinus discovered by Jeffrey in the 

 Tertiary rocks of New Jersey in which the short- 

 shoots are elongated and bear a considerable number 

 of spirally-arranged "needles." Here, at any rate, 

 is a case where the indications afforded by an abnor- 

 mality in a modern plant are fully confirmed by the 

 facts of paleobotany. 



In this place may be mentioned the important dis- 

 covery made by Von Mohl concerning the " double 

 needle " of the umbrella pine (Sciadopitys verticillata) . 

 He showed that its origin is precisely the same as that 

 of the seminiferous scale of the Abietinese, viz., from 

 the first two leaves of a secondary axillary shoot 

 which have become fused by their inner and posterior 

 margins ; as a result of which the ventral surface of 

 the organ is directed outwards. In this way the 

 eccentric orientation and structure of the " double 

 needle " is readily explained. Masters and Carriere 

 described an abnormality in which the " needle " was 

 deeply forked and from the fork sprang a short axis 

 bearing a whorl of " needles." Masters regarded the 

 " needle " as of axial nature ; but this abnormality is 

 probably best interpreted as the result of the elon- 

 gation of the otherwise suppressed axis of the short- 

 shoot bearing the two leaves fused by their posterior 

 margins, causing a separation of the leaves, while the 

 axis remained for part of its length fused with one of 

 its two leaves, and after becoming free higher up, 

 produced fresh leaves. The " double-needle " repre- 

 sents two leaves of a short-shoot which has become 

 much more reduced than in the case of Pinus, with 



