Evans: Notes on genus Herberta 205 



Lindb. ; in this species, according to Andreas, the wall is composed 

 of seven or eight layers and has a thickness of 130^1. In all 

 these forms he describes local thickenings in the cells of all the 

 layers. In the innermost layers the thickenings are in the form 

 of half rings extending across the inner tangential wall (see Text 

 FIG. 10) In the other layers they are in the form of bands on the 

 radial walls. Even here, however, the bands sometimes extend 

 to a greater or less extent along the tangential walls. According to 

 Andreas the structure of the capsule wall in the leafy Hepaticae 

 shows comparatively little variation, and the genus Herberta 

 agrees on the whole with his account. It might be added that 

 the valves are covered on the outside by a granular wax-like de- 

 posit, and that secondary splits sometimes occur in one or more 

 of the four primary valves. 



Many years ago Spruce* described the occurrence of rudimen- 

 tary shoots on the leaves of Herberta. According to his account 

 they arise singly or in pairs from the cells of the vitta in the basal 

 portion of the leaves and never in the divisions. These shoots 

 have not been observed by the writer and are probably developed 

 under exceptional conditions. They represent the only type of 

 vegetative reproduction known in the genus. As Spruce's figures 

 clearly show, the shoots bear three ranks of small bifid leaves and 

 show no signs of dorsiventrality. They resemble in many 

 respects the adventive shoots borne on the leaves of certain species 

 of Plagiochila, although they are much less abundantly produced. 



Revision of the species known from Europe, Canada and 

 THE United States 



According to most recent writers on the Hepaticae the genus 

 Herberta is represented in Europe by only two species. The first 

 of these is H. adunca (Dicks.) S. F. Gray, the type of the genus; 

 the second, H. Sendtneri (Nees), sometimes known as H. stra- 

 minea (Dumort.) Trevis. The range of H. adunca, according to 

 available records, is restricted to Norway, the Faroe Islands and 

 the British Isles; the range of H. Seridtneri is even more circum- 

 scribed, being accredited only to the Austrian and Bavarian Alps. 



* On the branch-bearing leaves of Jungermannia juniperina, Sw. Phytologist 2: 

 85, 86. 1844. [Illust.l 



