Febeuaey 15, 1907] 



SCIENCE 



271 



Two views are held in regard to the 

 medulla in the stems of the Filicales, one 

 that it is of stelar, the other that it is of 

 extrastelar origin. These two conceptions 

 lead to two divergent views of the stele — 

 to the two leading stelar hypotheses. 



The author of this paper holds to the 

 view that the medulla is of extrastelar 

 origin — excepting the parenchymatous tis- 

 sue that may appear in the center of the 

 stele at the base of seedlings in certain 

 cases. The following facts seem to favor 

 the correctness of this view: (1) The simi- 

 larity of cortical and medullary tissues. 

 (2) Their continuity through foliar and 

 ramular gaps. (3) The 'intrusion' of the 

 cortex above the origin of leaf traces near 

 base of many filicinean seedlings. (4) The 

 actual enclosing of a portion of the cortex 

 to constitute a pith at the base of adven- 

 titious shoots, where a protostele passes into 

 the siphonostelic condition — here described 

 for the first time, and apparently a direct 

 demonstration of the point in question. (5) 

 It has been shown recently that the meri- 

 stematic areas at the growing point do not 

 correspond to certain exact areas in the 

 mature portion of the stem — thereby one 

 of the arguments in support of opposing 

 view is removed. 



Polysfely in the Orchidacece: J. H. White, 

 University of Toronto. (By invitation.) 

 Van Tieghem affirmed that the eauline 

 steles of many plants repeatedly bifur- 

 cated, resulting in the phenomenon of poly- 

 stely. He further affirmed polystely does 

 not occur in roots, and that multistelie 

 roots of many orchids result from the con- 

 crescence of monostelic roots. 



His first statement has been disproved 

 by Leclerc du Sablon, Jeffrey, etc. 



The author of this paper takes ap his 

 second affirmation and shows that true 

 polystely does exist in orchid roots, and 

 that concrescence is not the correct ex- 



planation of the phenomena obtaining in 

 them. 



A large number of forms have been ex- 

 amined and conclusions have been based on 

 the following facts: (1) The root apex is 

 always covered by a single root cap, and at 

 the tip a single primary dermatogen, 

 periblem and plerome are to be found. (2) 

 In some orchids the lateral roots are always 

 monostelic. (3) In others they are mono- 

 stelic at their base. (4) In the most com- 

 plicated cases there are fewer steles at the 

 base than farther out from the stem bi- 

 furcation of the steles is the rule. (5) 

 The root initials consist of a single meri- 

 stematic mass for each root, no indication 

 of the concrescence of initials. (6) The 

 ground tissue in mature roots show no signs 

 of concrescence. (7) The roots in the 

 youngest generations tend to be monostelic. 

 An increasing complexity noted in succeed- 

 ing generations. Certain forms examined 

 lend support to the view that the medulla 

 in some cases is of extrastelar homologies. 



The Araucarie(B—A ' Proto-Siphonagamic' 

 Method of Fertilization: Egbert Boyd 

 Thomson, University of Toronto. 

 In my study of the megaspore membrane 

 of the gymnosperms, supernumerary nuclei 

 in the pollen tube of the Araucariea are re- 

 ferred to and the isolated position of the 

 subgroup indicated. The ancient geolog- 

 ical and the widely separated geographical 

 distribution, the large microsporangiate 

 cones in comparison with the megaspo- 

 rangiate, the evident transition between 

 sporophylls and foliage leaves (points re- 

 ferred to recently by Professor Seward) 

 are indications of an interesting and prob- 

 ably primitive group. The morphology 

 and anatomy of the micro- and megasporo- 

 phylls indicate that they are homologous 

 structures, functionally differentiated. The 

 microsporangium is fern-like. The micro- 

 spore multicellular, and the pollen tubes 



