T. Holm — Isopyrum biternatum. 135 



tuberous portion with, long and slender, filiform apex, but in 

 older plants a vertical and very thick subterranean stem devel- 

 ops from the crown of the root, bearing numerous basal leaves 

 and flowering stems. The ceespitose 1. micro phyllum Royle 

 possesses a long and stout subterranean stem with exceedingly 

 short internodes and covered with rigid libers from the with- 

 ered leaves ; in I. stoloriiferum Maxim, the rhizome is very 

 thin and stoloniferous with capillary roots, while in the Euro- 

 pean 7. thalictroides L. the roots are very slightly tuberous at 

 the base. Finally the inflorescence is somewhat different, and 

 as stated by Maximowicz the seeds exhibit a very distinct 

 structure in several of the species. A study of a more copious 

 material, and especially of the Asiatic species, would, no doubt, 

 add many points in regard to the external structure in general, 

 that of the rhizomes for instance. There is thus in Isopyrum 

 as understood by recent authors, Maximowicz and Franchet, 

 some certain variation noticeable in the structure of the floral 

 and vegetative organs, which seems to point toward generic 

 distinctions, and it would be very interesting indeed to know 

 whether this variation is accompanied by divergencies in the 

 internal structure. If the anatomical study of these species 

 should reveal facts of the same importance as those known 

 from the external structure, there is no doubt that the genus 

 would need a thorough revision, and evidently have to be 

 divided ; Leptopyrum and Enemion might, perhaps, prove to 

 be tenable, not speaking of the remarkable 1. stipitatum. The 

 seedling of I. thalictroides has been described by Winkler ;* 

 the cotyledons are hypogeic, and remain enclosed within the 

 seedx There is a distinct hypocotyl, which increases in thick- 

 ness, and the primary root is strong and ramified ; secondary 

 roots become developed from the axils of the cotyledons. The 

 first leaf succeeding the cotyledons is membranaceous and 

 sheath-like, while the second shows the normal form with three 

 green leaflets. A seedling of I. biternatum has been figured 

 by MacDougal ;f it shows a long primary root, and the cotyle- 

 dons are free and provided with long petioles. The two 

 first leaves, succeeding the cotyledons, have only rudimentary 

 blades, while in the third leaf three small leaflets are devel- 

 oped. The seedling of 1. biternatum as figured by Mac- 

 Dougal is, thus, very different from that of I. thalictroides. 

 Unfortunately MacDougal does not describe the seedling, and 

 the figure does not seem to have been carefully executed. 

 But so far the internal structure has only been considered 



* Die Keinipflanze des Isopyrum thalictroides L. (Flora, 1884, p. 195, with 

 plate III). See also Irmiscli : Beitrage znr Naturgeschichte des Melittis 

 Melissophyllum (Bot. Zeitung, 1858, p. 238). 



f Minnesota Bot. studies, 1896, p. 501. 



