INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 605 



contains 48 slides, very neatly mounted and secured in a suitable 

 box. These slides are intended to illustrate groups of lichens, and to 

 be of use also in teaching amateurs and beginners the outlines of 

 lichenology by making the appearance of the different parts of 

 lichens familiar to the eye. Special care has been taken to exhibit 

 the final organs of reproduction — the spores — of much use in determin- 

 ing the systematic position of lichens; and we may venture to sug- 

 gest that a similar attention to tlie eax'lier stages of the reproductive 

 organs and the thallus would improve futui'e fasciculi. A consider- 

 able number of the sj)ecimens are rare, or recently discovered in 

 Britain, and from this point of view will be interesting to the expert 

 lichenologist Such a series as this must be of more use to the 

 microscopist for the purposes of reference than the illustrations of 

 any lichenological work we know of. We have had the opportunity 

 of examining, at the British Museum, a parallel series of slides of 

 Alga) and Hepaticfe. 



Algae. 



Structure and Mode of Reproduction of Cutleriacese.* — The 

 history of development of the Cutleriaceae has been carefully fol- 

 lowed out by Reinke in the cases of Cutleria multifida, Zanardinia 

 collaris, and Aglaozonia reptans. 



As regards the vegetative development, he finds that the margin 

 of the thallus becomes dissociated into a number of thi-eads, which 

 he calls " cilia," a term obviously open to objection. At the basal 

 part of these threads is a meristem ; and here the threads coalesce 

 into a solid thallus. The increase in breadth of the frond is due 

 to branching of these threads. The reproductive organs of Cutleria, 

 Reinke terms autheridia and oogonia. The former, arranged in 

 groups on the thallus, are septated chambers placed on a multi- 

 cellular pedicel. The antherozoids are formed in pairs in a cell. 

 The oogonia, which occur on separate plants, are far less numerous. 

 They resemble the antheridia in form and arrangement, but are 

 considerably larger. From them are developed sixteen or thirty- 

 two oospheres, which escape in the form of biciliated swarmspores, 

 to which the antherozoids attach themselves and disappear, probably 

 becoming absorbed in the substance of the swarmspores. These 

 lose their cilia and secrete a cellulose envelope ; their further 

 development has scarcely been traced. Thuret found the swarm- 

 spores germinate without assistance from the antherozoids. The 

 development of the thallus of Zanardinia agrees with that of Cutleria. 

 In addition to the sexual organs Reinke found "neutral spores" 

 formed in unicellular sporangia, which break up into four or six 

 pear-shaped swarmspores. The antherozoids force their way into the 

 oosphere, which then germinates. In Aglaozonia no sexual organs 

 were found, but non-sexiial sporangia similar to those of Zanardinia. 



These observations, and those of Gobel on Ectocarpus j seem to 



* ' Nova Acta Leop.-Carol. Akad. Naturf.,' xl. p. 37 ; see ' Bot. Zeit.,' xxxvii. 

 (1879) p. 142. 



t ' Bot. Zeit.,' 1878, Nos. 12, 13. 

 VOL. II. 2 s 



