THE SYSTEMATICS OF THE GYMNOSPERMS 



Bij RUDOLF FLORIN 



Hortus Bergianus, Stockholm 



Status by the Middle op the Nineteenth Century 



When A. P. de Candolle (1813) had developed his theory of the natural 

 classification of plants on the basis of comparative and correlative morphology, 

 great activity set in in this field. But the wealth of taxonomic suggestions was 

 not coupled with a correspondingly deeper understanding of plant relation- 

 ships. Little was yet known of the true position of the gymnosperms, or of the 

 mutual relations of their several groups. The idea of the constancy of species 

 was still prevalent, and taxonomy lacked the background of any evolutionary 

 or phylogenetic theory. 



A new period in the history of botany had been initiated even before 1850, 

 inter alia, by the advance in microscopy and plant microtechnique. In 1842 

 a theory of the structure and homologies of the female conifer cones was put 

 forward by Braun (cf. Pilger, 1926). He considered the ovuliferous scale to 

 consist of an axillary shoot, the two lowest leaves (carpels) of which had fused, 

 apparently forming a single organ. As regards the male conifer organs, Braun 

 as well as Mohl (1845) stressed their character of single flowers. Brown's studies 

 of the female organs of the conifers and cycads, and especially his opinion of 

 their gymnospermy (1825, 1844), led ultimately to the bringing together of 

 these plants into what was regarded as a natural group, separate from the dico- 

 tyledons. In contradistinction to the angiosperms, the conifers and cycads were 

 supposed to have naked ovules equipped with an integument. The phyllotaxis 

 theory of Schimper and Braun (Braun, 1831, 1835) — a characteristic prod- 

 uct of idealistic morphology, based on the assumption of a spiral tendency in 

 plant growth — provided floral morphology and phyllotaxis with new means 

 of expression. 



As early as 1833 Mohl demonstrated the agreement between the sporangia 

 of the pteridophytes and the pollen-producing organs of the phanerogams, thus 

 to some extent paving the way for Hofmeister's discoveries. Having devoted 

 himself to the study of mature tissues, he later (1845) also explored their de- 

 velopment. The necessity of such studies as a basis of histology and compara- 

 tive morphology was emphasized by Schleiden, whose principal work (1842- 

 1843) greatly influenced progress. ]\Iohl was the first to investigate the de- 

 velopment of vascular ])undles and to observe cell division; he studied cell wall 

 formation, advancing the so-called apposition theory (1853), and demonstrated 

 (1851) in accordance with Schleiden's opinion tliat the cell is the primary 

 structural element of the plant body and that this body consists wholly of cells. 

 Nageli (1844-1846) also contributed in laying the foundations of essential parts 

 of cytology. According to him the growth of the cell wall is by intussusception. 



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