XXIV PREFACE. 



ordinary leaves, resting buds, which had two bud-scales, 

 and therefore resembled, in this respect, not the "Geitzen," 

 but the " Lotten." The derivation of the "Lotten" from 

 the "Geitzen" in the way described, does not occur 

 until the later degrees of ramification. 



To the examples mentioned in the note, p. 114 of Fern 

 leaves, with the apex of the leaf constantly undeveloped, or 

 only unrolled after long interspaces and in steps, belongs 

 also the genus Neurolepis, the larger species of which, re- 

 lated to N. exaltata, develope their slender pinnate leaves, 

 which often attain a length of 4 or 5 feet, in several 

 annual stages or lengths, which are marked in the deve- 

 loped leaf as contracted places, furnished with shorter 

 pinnae. In N. neglecta, Kiinze., the commonest species 

 of our gardens, I found four such sections, of which, 

 however, two often appear to be developed in one year. 

 With this mode of development is connected the fact 

 that the leaves of the species of 'Neurolepis ordinarily exhibit 

 a little rolled-up knob at the end, and only rarely their 

 proper leaf-point, running out into a terminal pinna. 



I have to give a short postscript to the natural history 

 of the Chlamidomonada, relating to the "resting stage" of 

 Chlamidomonas tingens (p. 215). The said species 

 appeared in great abundance this spring in little rain 

 pools, close to the town, colouring the water bright green. 

 When the " rest" commenced, the cells collected together 

 in pulverulent, partly floating masses, exhibited a 

 globular form, a diameter of from -^ to ^ of a millim., 

 granular-punctate, green contents, and one larger vesicle. 

 When the pools dried up in the month of May, crust- 

 like, pale brick-red coats were found on the ground, the 

 cells, formerly green, having assumed a pale reddish 



