'296 SUMMARY OF CURRENT RESEARCHES RELATING TO 



aerial leaf ; it is often destitute of stomates ; collenchyme has usually 

 more or less completely disappeared, and the palisade-parenchyme 

 entirely ; the vascular system is much smaller in amount, and of simpler 

 structure. Eeserve-substances are often present in abundance in under- 

 ground scales. Culture experiments showed that underground scales 

 may become transformed into organs having all the structure of ordinary 

 leaves by placing them under the normal conditions of air and light. 



Variegation.* — H. Timpe describes in detail the morphological 

 peculiarities of variegated leaves. The colourless areas are thinner than 

 the coloured ; this is usually the result of a diminished production of 

 palisade-parenchyme and a reduction of the intercelluiar spaces ; these 

 are closely associated with the disappearance of chlorophyll. When 

 young leaves have a red tinge, or when leaves are permanently red, or 

 turn red in the autumn, the coloration is confined to the areas destitute 

 of chlorophyll, or is strongest in them. The colourless areas usually 

 contain more tannin than the green. Starch is, under ordinary con- 

 ditions, stored up only in the green mesophyll ; while reducing sugar is 

 present in both areas, most abundantly in the colourless. 



Phyllodes of Acacia.f — P. Ledoux has studied the structure of the 

 foliar organs in those species of Acacia in which the leaves are replaced 

 by broad flat petioles of a deep green colour. The earliest leaves usually 

 have, in these species, a small number of pairs of leaflets, which drop early. 

 The older the plant the more completely are the ordinary leaves replaced 

 by these phyllodes, which are persistent from year to year. From their 

 colour, their flat form, and the abundance of stomates, it is clear that 

 they perform the ordinary function of leaves. They present also special 

 characteristics in a thickened cuticle, abundant sclerenchyme, and a 

 well-developed aquiferous tissue, which adapt them to resist excessive 

 transpiration and to store up a large quantity of water in their tissues. 



Tendrils of Lathyrus. $ — K. Fritsch discusses the value of the 

 presence of tendrils as a character for the subgenera of this genus, and 

 decides against it as of any phylogenetic value. Among allied species 

 there are all intermediate conditions between species with well-developed 

 leaf-tendrils and others where they are entirely wanting. The genus 

 Orobus must be entirely suppressed. The author adopts five out of the 

 six sections of the genus proposed by Godron. 



Outgrowths of Hibiscus vitifolius. § — A further examination of 

 these structures leads Miss Elizabeth Dale to the conclusion that they 

 develope only when transpiration is reduced, and that they are formed 

 chiefly on organs which are actively assimilating. They occur only on 

 plants in which there is an accumulation of starch ; and their formation 

 is accompanied by the production of oil, which is not found in normal 

 leaves. 



Tricotyledony.il —E. Gain gives a long list of Dicotyledons in which 

 the embryo occasionally has a third cotyledon, and then describes the 



* Beitr. z. Kenntn. d. Pauachirung, Gottingen, 1900, 124 pp. See Bot. Cen- 

 Iralbl., lxxxv. (1901) p. 75. f Comptes Rendus, cxxxii. (1901) pp. 722-5. 



X < >esterr. Bot. Zeitschr., 1. (1900) pp. 389-96. 



§ Proc. Boy. Soc, Ixviii. (1901) pp. 16-19. Cf. this Journal, 1900, p. 348. 

 || Rev. Gin. de Bot. (Bonnier), xii. (1900) pp. 369-93 (1 pi. and 18 figs.). 



