1883] 



MICROSCOPICAL JOURNAL. 



95 



Ciliary Motion as Accompany- 

 ing Asexual Reproduction in Cryp- 

 togams. — The motile cells concerned 

 in asexual reproduction in plants have 

 been named swarm-sporesor zoospores. 

 'J'hese result from the contraction of the 

 protoplasmic contents of certain cells, 

 and its reconstruction into primordial 

 cells, which escape from the mother 

 cell either by openings, or by the dis- 

 solution of its walls. When liberated 

 under suitable conditions the naked 

 swarm-spores move with a rotary and 

 progressive movement, the rapidity of 

 which has been shown by Hofmeister * 

 to be considerable. For example : 



Mtn. per second. 



Fiiligo 7'ariafis, .7 to .g 



Lycogola epidcndnim, .t^t^ 



CEdogonium7'Csicatum, .15 " .20 



Vauchcria sp., .10 " .14 



In some cases rotation has been 

 noticed before the swarm-spores have 

 left the mother-cells, a phenomenon 

 corresponding exactly to the move- 

 ment of the embrvo within the ovum, 

 (mollusca, &c.,) brought about by 

 vibration of cilia, which are perfectly 

 distinct. The duration of activity 

 among swarm-spores is variable, rang- 

 ing from one half, to one and a half 

 minutes only in Vaucheria, up to a day 

 or two in the myxomycetes. 



The advancing movement, as well 

 as the rotation about the longer axis, 

 is occasioned by the rapid vibratory 

 motion of extremely small, whip-like 

 extensions of the hyaline portions 

 of the protoplasm. These delicate 

 threads are often very numerous, as in 

 Vauiheria, where the primordial cell 

 on escaping from zoosporangium is 

 found to be covered everywhere by 

 delicate, densely crowded, short cilia. 

 In other cases (oedogonieae) they form 

 a crown or crest encircling the hyaline 

 anterior extremity of the zoospore, 

 while more commonly there are but 

 two cilia, usually very long, which 

 are attached at the same point on 

 the margin of the zoospore. 



* " Lehre von der Pflanzenzelle," p. 30. 

 (Vide ref. 103. ) 



In the myxomycetes and monoble- 

 pharidae, however, we find but 

 one long cilium, while in Sapro- 

 Icgnia proper there may be, eiiher 

 one before and one behind of 

 unequal lengths, or two of equal 

 length in front. It should be 

 borne in mind that all swarm-spores 

 are not ciliated, for, in the myxo- 

 mycetes and Peronospora we see them 

 endowed with amoeboid movement, 

 and in tne Hydrodyctieaj the larger 

 swarm-spores never leave the cell in 

 which they have been produced. The 

 zoospores produced by a single 

 mother-cell vary from five {Cystopus) 

 to one hundred thousand, (small 

 swarm-spores of hydrodyctieai) — the 

 possession of vibratile cilia renders 

 their dissemination a comparatively 

 easy matter, water alone being 

 needed, which, in the case of non- 

 aquatic cryptogams, is furnished by 

 rain. 



On watching the swarm-spores swim 

 about for a time, two individuals will 

 be seen approaching each other ; thev 

 will meet, coalesce, lose their cilia, and 

 proceed in the regular course of asex- 

 ual reproduction, which may easily be 

 observed by sowing the pseudospores 

 of Cystopus in water on a glass slip. 

 Of special interest in the study of 

 vibratile cilia, are the zoospores pro- 

 duced by sowing the- conidia of 

 Peronospo7'a mfestans., the mould 

 which produces the potato murrain. 

 Germination is favored by darkness, 

 and will commence in from one and 

 one half to three hours, the ciliary 

 movement continuing from fifteen to 

 thirty minutes. 



Ciliary Motion as Accompanying 

 Sexual Reproduction in Crypto- 

 gams. — In the sexual reproduction of 

 plants only the male cells are en- 

 dowed with motion, being known as 

 male- or sperm-cells, antherozoids or 

 spermatozoids. They are strictly 

 homologous with the sperm-cells of 

 animals, and resemble them closely. 

 These male, motile fertilizing bodies 

 consist of naked protoplasm, and are 

 considered to be primordial cells. 



