18 GEi^F ZU SOLMS-LAUBACH— MO^'OGEAPH OP THE ACETABULAEIE.^:. 



^^ liole slioot (compare tlie figures, Plate I. figs. 4, 8, 12, of Acetahiilaria mediterranea, as 

 well as Plate TV. fig. 5, Saliconjne Wrightii). The thrusting towards the acroscopic side 

 happens through its excessive grow^th in size. 



A beautiful confirmation of what has just been said came into my hands after the text 

 of this paper had been prepared. A young specimen of A. Feniculus was examined, in 

 which immediately beneath the cap, normal in all respects, there w^as a whorl of hairs 

 which attracted my attention from the vesicular form of its branches. Closer exami- 

 nation resulted in disclosing a very remarkable anomaly (Plate II. fig. 2). Among the 

 short shoots of the whorl in question there were single ones of quite normal character, 

 polychotomous, provided with cylindrical, hair-like, long cells of the same order as the 

 bi'auches. Most of them, however, w^ere transformed into arrested fruit-discs. The 

 stalk was formed of the primary branch of the short shoot ; its secondary branches were 

 shortened and bore at the apex in place of the tertiary outgrow^ths, as a rule, one 

 terminal, short, papilla-like cell, rarely two inserted together. That these represent the 

 branches of the third degree there could be no doubt. The sporangial ray appeared as a 

 more or less developed knob, sometimes constricted at the base and vesicular above, on 

 the basiscopic side of each of the secondary branches of the short shoot ; it never attained 

 complete development, and always persisted in a distinctly lateral position. We have to 

 do here, then, with the formation of caps of a higher order, since the secondary branches 

 of the short shoot undergo the same alteration as occurs otherwise only on the primary 

 ones. By a farther development of the anomaly we should have a plant of which the 

 terminal fruit-disc would be surrounded by a complete whorl of similar lateral ones. 

 Perhaps Woronin's observation of a branching Acetabularia mediterranea in which each 

 branch bore a cap may be explained in this w ay ; or, on the other hand, it may be only a 

 fasciation-like forking of the stalk of the apex. 



Among the Cymopolieoi we meet with a farther difi'erence of organization, in w-hich 

 the two other groups do not share, in the absence or presence of spore-formation in the 

 sporangia. We have to thank Cramer for a criticism of the systematic significance of 

 this character. He makes out that we are compelled, in the employment of this 

 character for the classification of the Order, to separate the neighbouring genera Botryo- 

 pJiora and Dasycladus, Neomeris and Cymopolia. That these two groups of genera, of 

 which one is incrusted and the other is not, have been farther differentiated in analooous 

 fashion is scarcely doubtful. But which of the divisions of each of these two groups is 

 the original one, w hich the more strongly modified and the more advanced ? 1 am of 

 opinion that one may not doubt, with reference to the alternation of generations of sexual 

 and asexual individuals so general among the Chlorojiliyceai, that those forms in wdiich it 

 fails, in spite of the apparent simplification of the course of development, are still the 

 most modified phylogenetically. So in this case Dasycladus, in which the sporangia, inter- 

 mitting the spores, directly produce gametes, the product of the conjugation of w hich I 

 saw grow directly into a normal young plant ; Cymojmlia, where possibly sexuality has 

 been lost, and only vegetative germination of the m hole sporangia retained — provided that 

 in the case of the preceding observations (Solnis) we have met with no abnormahty. 

 Dasycladus would stand in some such way to Botryo^^liora as CymopoUa to Neoiueris. 



