140 Professor Alexander Dickson on the 



in this remarkable conifer were regarded simply as leaves 

 until, in 1866, I pointed out that they were placed in 

 the axils of scale-leaves, and that they differed essentially 

 from the few foliage-leaves which occur in the young 

 plant, in having two vascular bundles, one on either side 

 of the middle line, instead of the single mesial bundle or 

 midrib exhibited by the foliage-leaves. I concluded that 

 these "needles" should be referred to the category of 

 phj'lloid shoots or cladodes.* 



In 1868, Dr Engelmann propounded the view that the 

 " needle " of Sciadopitys consisted of an aborti've axillary 

 shoot, developing two leaves which had become fused 

 together.! According to this view, the structure would 

 be comparable to the bifoliar spur or fascicle in Finns 

 syhestris, with connation of the two leaves. 



In the same year, M. Carriere % described monstrous 

 Sciadopitys " needles " where the slightly bifid character 

 of the extremity of the ordinary "needle" had become 

 much pronounced, and where a bud was developed from 

 the interval between the two points. 



In 1871, Von Mohl published an elaborate and admir- 

 able investigation of the stiucture of these " needles."§ 

 He discovered that in the two fibro-vascular bundles the 

 arrangement of the elements was such that the phloem 

 was directed towards the upper and the xylem towards the 

 lower surface of the "needle;" and, taking this in con- 

 nection with what was previously known regarding the 

 squama fruct if era, he came to the conclusion that in the 

 Sciadopitys " needle," just as in the squama fructif era, we 

 had to deal with an abortive secondary shoot developing 

 two leaves which become united hj their posterior margins, 

 and thus have their morphological lower surfaces directed 

 upwards. 



In 1872, Strasburger described the development of the 



* " On the Phj'Uoid Shoots of Scwihjpitys verticillaia," Beport of Internal. 

 Horticidt. Exhibition and Botanical Congress, London, 1866. Also in Jouriial 

 of Botany, iv. (1866) p. 224. 



t Engelmann, SitzungsbericJite d. Katurforsck. Freunde, Berlin, 1868, p. 

 14. Also in Bat. Zeitung, 1868, p. 484. 



X Bcvvc Horticole, 1868; as referred to in Gardeners' Chronicle, May 2 1868, 

 and March 1, 1884. 



S H. V. Mohl, " Morphologisohe Bftrachtun<r dtr Blatter von Sciadrpitys," 

 Bot. Zcitvng, 1871, p 1. 



