138 SCIENCE PROGRESS. 



limit of the cylinder, and thus brings into greater promi- 

 nence the idea, already clearly stated in 1872, of an indi- 

 vidualised stem cylinder in direct continuity with that of 

 the root. 



The term has eventually, though very slowly, found 

 its way into general use. 



In 1884 Morot, a pupil of Van Tieghem, published the 

 results of a research (6) devoted to a comparative investiga- 

 tion of the pericycle in both root and shoot. 



The publication of Morot's paper brings to an end what 

 we may call the first phase in the development of the stelar 

 idea. 



SECOND PHASE— POLYSTELY AND ASTELY. 



The second phase was inaugurated in an investigation (70) 

 by Van Tieghem and his pupil Douliot, of the anatomy of the 

 stem of various species belonging to the genus Primula. Their 

 observations were carried out on a number of new species from 

 the East, as well as on many old species, making together a 

 total of 114. They resulted [yd) in a division of the aggre- 

 gate genus Primula L., into two segregates, Primula Tourn. 

 and Auricula Tourn., as had been already done by Tourne- 

 fort, but now based on a fundamental difference in the 

 structure of the stem of the two segregate genera. While 

 the stem of the species belonging to Primula possesses 

 a single normal central cylinder in its whole extent, the 

 narrow cylinder of the hypocotyl of an Auricula, instead 

 of dilating in the ordinary way above the level of the coty- 

 ledons, gives rise by successive bifurcations to two or more 

 vascular strands, each surrounded by an endodermis and 

 possessing" the structure of the single hypocotyledonary 

 cylinder. In the genus Gunnera {Haloragece) a similar 

 state of things obtains. These facts were, in the main, 

 already known, having been investigated by Vaupell, 

 Kamienski and Reinke. The opinion of these authors 

 was, however, that the separate vascular strands were vas- 

 cular bundles of the " concentric " type with peripheral 

 phloem, comparable for instance to those found in the 

 cortex of certain Mclastoniace<z ; and this was the view 



