446 SUMMARY OF CURRENT RESEARCHES RELATING TO 



parenchyma ; these substances also occur in the assimilatory tissue of 

 the leaf. An exchange of material seems to occur between the reserve 

 parenchyma and the latex-carriers on the one hand, and between the 

 latter and the assimilatory tissue on the other. The latex tissue of the 

 Euphorbiaceae, which is generally regarded as purely excretory, should, 

 in the author's opinion, be regarded rather as a conducting system for 

 the transport of a part at least of the material elaborated in the leaves. 

 Many of the Euphorbiaceae have tannin-carriers composed of equal 

 cell-elements, which, like the latex-carriers, are continued from the 

 stem into the leaf. By absorption of their transverse walls they may 

 be transformed into tubes often of considerable length. Their develop- 

 ment is most marked in the Phyllanthoideas. 



Morphology and Anatomy of Azorella Selago.* — C. Ternetz gives 

 an exhaustive account of this interesting little Umbellifer, which forms 

 a characteristic feature of the flora of Kerguelen's Land and other 

 islands of the Southern Ocean, where it forms dense low-growing 

 cushions. In growth and structure it is a well-marked xerophyte. 

 The climate is remarkably damp, but owing to the constant low tem- 

 perature, absorption of water from the soil is checked, while owing to 

 the almost uninterrupted strong winds, rapid transpiration is favoured. 

 In its stem-structure it differs remarkably from the description given 

 by Drude for the genus in that it possesses a cambial secondary growth 

 (which in the older plants is anomalous), while the vascular system 

 forms a loose ring, not limited by a phloaoterma ; moreover crystal-sacs 

 are absent from the pith, and there are no woody hard-bast strands in 

 the cortex. 



Air-roots of Avicennia tomentosa.f — W. Brenner has studied in 

 detail the anatomical structure of the vertical air-roots of this mangrove 

 in material from West Africa. The structure demonstrates to the full 

 their respiratory function, and the alteration with increased age and 

 size of the roots represents the response of the plant to increased need 

 for gaseous interchange. For instance, while the young roots have a 

 smooth exterior and show but little phellogen development, the older 

 show this in a marked degree, and their surface is rendered uneven by 

 the formation of numerous lenticels. 



Origin of the Seed-leaf in Monocotyledons.! — E. Sargant has 

 examined the course of the vascular bundles in a number of seedlings 

 representing a series of typical Liliaceous genera, and concludes that 

 the most primitive form is that represented in Anemarrhena. The 

 arrangement is a symmetrical one. The bundles run the whole length 

 of the cotyledon, and are placed approximately at the foci of the 

 elliptical transverse section of the organ. The transition stage in the 

 short hypocotyl is also a perfectly symmetrical one. Each xylem group 

 gives off three branches of protoxylem, and each phloem group divides 

 into two. The four lateral branches of protoxylem fuse in pairs, to 

 form the regular tetrarch stele of the root. If this be compared with 

 Eranthis, a genus of Ranunculaceae, the resemblance of the ground plan 



* Bot. Zeit., lxx. (1902) pp. 1-20 (1 pi. and 8 figs.). 



* Ber. Deutsch. Bot. Ges., xx. (1902) pp. 175-95 (3 ph.). 

 % New Phytol., i. (1902) pp. 107-13 (1 pi.). 



