596 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the intercellular spaces are very large, this internal arrangement pr< 

 that the aerobic generation must develop an extraordinary degree of 

 transpiration, which indeed is seen in the stomata." 



Scapania paludicola.* — L. Loeske writes on the question of parallel 

 forms in mosses. He has observed that two different species produce 

 parallel forms under similar conditions of life. These two species are 

 Scapania undulata and S. irrigua, and the respective parallel forms are 

 var. paludosa 0. Mull, and var. nova paludicola L. Loeske. These two 

 forms may be distinguished by the always evenly thickened cell-walls of 

 the leaf of 8. undulata, and the always triangular cell-thickenings of 

 8. irrigua. These differences are hereditary. Both parallel forms show 

 the same feeble growth, pale-green colour, the same markedly crumpled 

 arc-shaped commissure, and live in elevated swamps. What is the origin 

 of parallel forms of such great similarity ? Two conditions are neces- 

 sary : the respective species must be closely allied, and must have similar 

 conditions of life. Further, they must be very variable species and 

 easily influenced by water. Both these considerations play a great part. 

 If 8. irrigua had not the fixed hereditary character of forming triangu- 

 larly thickened cell-angles, even in the most difficult conditions of life, 

 it would often be impossible to separate 8. paludosa from S. Mulleri. 

 In Philonotis one can often only guess at the relationship of a water- 

 form. S. paludicola is perhaps only a form in the making. It may be 

 that the rank of a species is due to it, in the 0. Muller sense, as is the 

 case with 8. paludosa C. Mull. The author found his new " species " in 

 the Upper Hartz, and it is also known to him from the Algiiu and 

 Pommerania. A large part of the northern Martinellia paludosa as 

 defined by Arnell belongs to Scapania paludicola, not to S. paludosa. 



Sphagnum modified by Cold Water. f—E. Melin continues his 

 studies on the biology of Sphagnum, describing in his second paper some 

 cold-water forms of the genus, found in Angermanland. They were 

 varieties of 8. riparium. The older branches were bare and stiff, while 

 their axes had become green and taken over the function of the fallen 

 leaves. The leaves die gradually from their apex, dropping off bit by 

 bit, beginning at the base of the branches. The stiffness of the axes 

 is caused by a strong cellulose thickening of the cell-walls in the outer 

 portion of the central cylinder. The main stem becomes also very green 

 and functions as assimilative tissue. These cold-water forms grew in 

 and immediately in front of a spring, of which the maximum temperature 

 did not exceed + 6° C. In a higher temperature normal plants were 

 formed. The author attributes the peculiarity of form to the low 

 temperature of the water during the period of vegetation. Similar 

 forms of S. angustifolium, 8. apiculatum, 8. Girgensohnii and S. squar- 

 rosum were found under similar conditions of temperature. 



* Magyar Bot. Lapok., xiii. (1914) pp. 298-302. See also Bot. Centralbl., cxxix. 

 (1915) p. 259. 



t Svensk. Bot. Tidskr., viii. (1914) pp. 309-14 (3 figs.). See also Bot. Centralbl., 

 cxxix. (1915) p. 88. 



