s 



I 



1907] CURRENT LITERATURE 



3^3 



NOTES FOR STUDENTS 



^ 



Vegetation of the high Andes. — Weberbatjer draws this picture of the ancline 

 vegetation :^^ In the high Andes of central Peru most plants are not structurally 

 xerophilous, and dessication by the high altitude is much restricted by the abund- 

 ant precipitation and the prevalence of clouds. Were the danger of drying so 

 greatj one would expect that the moistest locations would bear the most species 

 and the most vigorous forms, and that on the moist ground the vegetation would 

 ascend higher than elsewhere. But the vegetation of the high Andes presents 

 no such picture; the high-andine moor contains fewer species than the meadows 

 of cushion and rosette plants, and none of those stouter forms which in their aspect 

 recall the lower regions — the shrubs, tufted grasses, and tall-stemmed herbs; 

 these grow by preference rather on the dry slopes, the stony ground, and the 

 rocks; and upon a stony substratum the limits of vegetation run higher than upon 

 well-watered ground. The explanation of these phenomena is to be sought, in 

 my opinion, in the temperature of the ground. By the low temperature of the soil 

 * many plants are kept away from the moors, while the simultaneous high tempera- 



ture of the rocks is favorable for vegetation. That temperature of the soil at these 

 elevations plays an important r61e is indicated by the horizontal position of 

 roots, referred to in an earlier paper, ^^ and by the very aspect of the vegetation. — 

 C. R, B, 



Transmission of tropistic stimulation.— Fitting^'' has undertaken to ascertain 



in what manner the tissues of perception and reaction are connected that the 

 stimulus indirectly determines the direction of the curvature. The work consists 

 mainly of a study of photo tropic response (coleoptile of the grasses, chiefly A vena) 

 as affected by more or less complete disconnection of the tissue between the apex 

 and base. Wounding by transverse incision or by splitting does result in a feeble 

 traumatic response, but neither the growth nor the capacity for perception and 

 response is significantly affected. It may be said that the reliability of the author's 

 conclusions hinges largely upon the truth of this statement, but the reviewer finds 

 no reason for doubt and the w^ork of Roxhert is in accordance with it. The 

 author shows that whatever course transmission is compelled to follow, the curva- 

 ture is entirely independent of the unilateral occupation of the perceptive organ 

 by the stimulus. Individual segments of halved or quartered' coleoptiles will 



nf thp ar>ex. Even in leaves from 



respond if the segment includes a small portion 



portion a large square of tissue has been removed, transmission 



occurs. The stimulation 

 organ. The author rega 



transmission 



sa Weberbatjer, A., Weitere Mitteilungen iiber Vegetation und Klima der 

 Hochanden Perus. Engler's Hot. Jahrb. 39:449-461. pis, 4, 5. 1907. 



sb 



Op. ciL 37:60 ff. 1905. 



Sc Fitting, Hans, Die Leitung tropistischer Reize in parallelotropen Pflanzen- 

 teilen. Jarhb. Wiss. Bot. 44:197-253. fig, 26. 1907. 



