254 ON THE PRESENT STATE OF OUR 



liappily keeping" within bounds in liis subdivisions. Besides Agbard's 

 work, we must mention the pubUcations of Harvey on the Antarctic 

 algae, the works of Postels and Ruprecht on the algge of the north 

 Pacific Ocean, and a number of monographs on single families or 

 floras. 1 can only name the most i mportant ; to enumerate them all would 

 lead me too far: the works of Smith and Ealfs on the British Dia- 

 toms and Besmids, that of De Barry on Conjugate, the beautiful es- 

 says of A. Brauu, and among the Austrians the excellent publications 

 of Grunow, especially on Diatoms. Finally, T must not forget to men- 

 tion that Dr. Eabenhorst has done much to promote the difi'us'iou of 

 accurate knowledge concerning;, the species of cryptogamous plants by 

 his work on the Cryptogamic Flora of Germany, and by his later publi- 

 cations, especially his dried collection of cryptogams. 



The structure of the vegetative organs of the small but interesting^ 

 group of Ckaracew was investigated by the interesting labors of Bischoff 

 and A. Braun. Thuret published important information concerning 

 the antheridia; Carl Miiller investigated fructification, and Pring- 

 sheim germination. Their classification was improved, especially by 

 A. Braun, from whose master hand we may expect a monograph of the 

 Characetc. 



If we now turn to the lichens, we will see that the views of the pe- 

 riod of Linne's system long remained in credit, and that reform was 

 late and gradual. Consequently the number of eminent discoveries 

 in this department has been smaller, and its organography is still far 

 from being satisfactory. Speersehneider, it is true, has furnished us 

 with some valuable data concerning the structure and manner of 

 growth of the thallus; but we are indebted for the most accurate in- 

 formation on this subject to Schwendener, who has published in two 

 dissertations the result of his investigations of shrubby and foliaceous 

 lichens. We know now that the thallus of lichens consists of three 

 different layers, an outer orenvelope forminglongfibrous cells, a middleor 

 gonidinm composed of roundish cells filled with chlorophyll, and an 

 inner or i)itli ot the same structure as the outer. The behavior of these 

 three layers, which was investigated particularly by Schwendener, fur- 

 nishes many points for classification. Korber has published an excellent 

 dissertation on the gonidia or generating cells of lichens. lie states that 

 these cells break through the envelope, become changed and converted 

 into the so-called soredia. These observations establish the fact that 

 the soredia are the organs of generation of lichens, and correspond to 

 the buds of higher plants. 



Many have studied the bowl-shaped fruit or apothecium of lichens, 

 but the data are scattered through different works. Tulasne's work, 

 "*S'Hr VAppareil Roprodnctenr dcs Liehencs,''^ is of special importance, 

 since it proves that lichens have another kind of fruit, forming small 

 dents and containing minute, straight, and narrow cells. They are 

 called spermagonia, and are probably the male organs of fructification. 



