places. If a definite number of hairs are formed on a leaf, these are closer 

 together in a given small area, because the epidermal cells separating them 

 are shorter. This partially explains why alpine plants appear to be less 

 pubescent when grown on plains. These plants grow more luxuriantly, the 

 dimensions of their organs become larger and the hairs are separated further 

 from one another. But. in fact, even in dry localities, an increased hair for- 

 mation takes place. Thus Moquin-Tandon' cites observations by Linneus. 

 that the Lady's Thumb (Polygonum Persicaria L.) seems very smooth at 

 the cc\gG of bodies of water, but beset with hairs in dr>' places. Our field 

 thyme (Thymus Serpyllum L.y loses its glaucous surface at the sea shore 

 and acquires a short, \\2i\vy covering. Our Turk's cap lily (Lilium Marta- 

 (/on L.) when cultivated for some time in gardens is glaucous, but becomes 

 pubescent again, like the wild plant, when grown on poorer soil, etc. Such 

 phenomena may be observed also in garden i)lants which, self-sown, grow 

 on sandy places in the fields. 



An unusual hair growth takes place, further, in many parts of plants 

 when they no longer develop normally. According to Moquin-Tandon. the 

 stamens of the triandrous bindweed are covered with thick wooly hairs. 

 The stamens of several kinds of Mullen (X'erhascum ) heha\e similarly if 

 the anthers become deformed. The peduncles of tlu- smoke tree ( k'lnts 

 Cotinus) are almost without hairs before blossoming and it they bear seed. 

 If, on the other hand, the fruit does not mature, the stems of the sterile 

 blossoms grow longer and numerous, long, \ iolet colored hairs appear on 

 them. The last-mentioned formation of hair does not belong among the 

 phenomena connected with drought, but should be considered as a process 

 of correlation. The water and nutritive substances, which should be utilized 

 in the maturing of the anthers or seeds, are used in a greater measure for 

 the benefit of other parts of organs, when the sexual organs are destroyed. 

 Possibly the phenomena recently observed in parthenogenesis belong in part 

 here, where the micropyle is stopped up as the result of the hair-like elon- 

 gated cells of the style tissue or of the integuments'-. 



Als(\ we find in the root system that pubescence varies according to 

 the place where the root is kei)t. In the same varieties, the whole system 

 can develop into the form of long, slender, whip-like, scantily branched, 

 bare, or almost bare roots, if the root axis dips into water or into porous 

 sand saturated with water. The root branches become shorter, more 

 knarled, branched and pubescent, the drier the soil is in general ; — the more, 

 therefore, that the root is obliged to depend only on the moist air of the soil 

 interstices. In air which is absolutely dry, the roots (according to Per- 

 secke'*), do not develop any more hairs. If the roots are exposed to moist 

 air, the young tips, just behind the growing apex, become very hairy, be- 

 cause almost every epidermal cell has pushed f)ut into a hair. 



1 Pflanzen-Teratologie, translated by Schauer, 1842, p. 61. 



- Winkler, H., LTeber Parthenogenesis bei Wikstroemia. I'.ei-. d, D. Bot. Ges., 

 .Tahrpr. 1904, Vol. XXII, p. 573. 



'•'• Persecke, Ueber die Formveranderuiig- der Wurzel in Krde und Wasser. 

 Inauguraldissertation, Leipzig 1877. 



