204 ON THE STEUCTUKE AND AFFINITIES OF CHARACE.E. 



" cystocarp " of the FloridecB, and (iuferentially ) in the fructifica- 

 tion or so-called "receiDtacle" of the Basidiomijcetes. In order to 

 make room for the Characea among Carpospurecc, Sachs has been 

 obliged to insert in the above extract an exception in then- case, 

 where, he says, the processes of growth alluded to "do not go very 

 far;" but even this guarded statement seems somewhat to overstep 

 the mark. The cortex or enveloj)ing tubes of the "nucule" of 

 Chara and Xitella are formed at an early period, and attain their 

 full development before fertilisation, simply hardening afterwards 

 into the black shell in which the germinating spore is invested. 

 The location of Characca among Oospores would be equally for- 

 bidden by many weighty considerations. 



If, therefore, we are compelled to exclude Characece altogether 

 from the group of Thallophytes, the only alternatives left are to 

 allow them to retam then- place as a distinct group co-ordinate 

 with Thallophytes, Miiscinecc, and Vascular Cryptogams, or to 

 place them among Miiscinea. The first of these alternatives has, 

 as we have seen, the sanction of some high authorities ; but are 

 there any sufficient reasons against the latter and simpler course ? 

 The remarkable resemblance of the antherozoids to those of 

 Mosses has been remarked by Thuret and others ; but it has appa- 

 rently been thought that the assumption of genetic affinity is 

 forbidden by other considerations connected with the reproductive 

 organs, and by the external form of the nutritive portion of the 

 plant. Too much stress should not, however, be laid on the latter 

 consideration, since within Muscinea, itself we have the transition 

 from the thalloid MarchantiecB to the frondose JungermanniecB and 

 Musci ; and the objection can hardly be sustained by those who 

 place Equisetacece and SelayinellecB within the same group, the 

 Vascular Cryptogams, and Basidiomijcetes and Floridece even within 

 the same class, the Carposporece. Among flowering plants it is 

 admitted that the most abnormal development of the nutritive 

 organs — adapting particular species or genera to live in exceptional 

 ckcumstances, as in the case of Myrioplujllum, Cuscuta, and Lemna, 

 — should not exclude them from location even in the same natural 

 order with plants which are otherwise nearly allied to them. Scarcely 

 any of the plants hitherto recognised as MuscijiecB are purely 

 aquatic ; and if we imagine a cormoph}H:e destitute of vascular 

 tissue gradually acquiring aquatic habits, the structure of Chara 

 would be a very likely one for it to attain ; the polysymmetry of 

 Characea: would aj)pear to result from analogous causes to the bilateral 

 symmetry of Hepatica. In the Sphaynacece, which nearly apin'oach 

 a true aquatic habit, we have a rudimentary cortication of the 

 stem reminding one somewhat of that of Chara. On the other 

 hand, the totally dissimilar structure, under somewhat similar 

 conditions, of Characea from that of FloridecB or Fucacete, seems to 

 indicate a wide genetic separation. 



One other point of resemblance may be noted between Characece 

 and MuscinecB, viz., that of the so-called "pro-embryo" of Chara 

 to the protonema of Mosses. But first of all, let me point out 

 what seems to me a misuse of the term "pro-embryo " in crypto- 



