1008 SUMMARY OF CURRENT RESEARCHES RELATING TO 



begin to bo formed on tho outer wall, and advance towards the 

 interior of tbe cell, tbc starch gradually disappearing. The seeds of 

 Lepidium sativum and ruder ale arc distinguished by a homogeneous 

 mucilage which escapes by diffusion ; while the mucilage of otber 

 seeds which swell up is always differentiated. This mucilage agrees 

 closely in its properties with cellulose ; and in the process of growth 

 mucilage is frequently transformed into cellulose, as in the case of 

 Erysim u m cheiranthoides. 



Endoderm.* — M. C. van Wisselingh points out the distinctions 

 between the endoderm and the bundle-sheath of the central cylinder 

 already described by him."|" The former is to be found immediately 

 beneath the epidermis or velamen in nearly all roots of Phanerogams 

 (it is wanting in Helleborus viridis) ; the latter appears to be in- 

 variably present. Although resembling one another in certain points 

 of anatomical structure, they differ in the endoderm never having tho 

 suberous layer which is always so characteristic of the sheath of the 

 central bundle. While the sheath consists of only a single layer of 

 cells, the endoderm is in all cases composed of at least two, and in 

 most cases is extremely well marked by the remarkable differentiation 

 of its cells into longer and shorter, the wall of the long cells resembling 

 that of the cells of bark, while that of the short cells is always very 

 thin, though sometimes considerably lignified. 



Conducting-tissue in some anomalous roots of Monocotyle- 

 dons.:]: — Herr M. O. Eeinhardt gives the following as the more im- 

 portant results of observations on this subject : — A union of the 

 separate parts of the two conducting tissues (hadrome and leptome) 

 is brought about most completely in the Pandanacese by the funda- 

 mental parenchyma. In tbe Cyclanthaceae the hadrome-bundles unite 

 into plates, anastomosing abundantly, and the same occurs in 

 Chamserops humilis and Areca rubra. The isolated leptome-bundles 

 do not anastomose so frequently ; the outer ones more often coalesce 

 with the peripheral, or the two inner ones into one. The leptome 

 communicates directly with the hadrome through breaks in the 

 mechanical tissue in the Musacese, Cyclanthacese, and some other 

 species. Hadrome-bundles completely isolated from the stem to the 

 growing-point of the root occur in a few cases. In some palms, two 

 kinds of such bundles are to be distinguished, one lying in the 

 mechanical ring, the other isolated in the fundamental parenchyma. 

 Isolated leptome-groups also occur occasionally. The inner paren- 

 chymatous cylinder is completely separated from the hadrome and 

 leptome in the root of many palms by mechanical cells. 



Mechanical Tissue-system.§ — Herr A. Tschirch proposes to apply 

 the general term Sclerenchyma-cells or Sclereids to all thick- walled 

 cells which are not Stereids or bast-cells ; and further to classify the 

 former as follows: — The sclereids in barks and fruits he calls 



* Arch. Ne'erl. Sci. Exact, et Nat., xx. (1886) pp. 427-48 (2 pis.), 

 t See tbis Journal, ante, p. 271. 



X Pringsheim's Jahrb. f. Wiss. Bot., xvi. (1S85) pp. 336-66 (1 pi.). 

 § Ibid., pp. 303-35 (3 pis.). 



