122 RECOKD OF CURRENT RESEARCHES RELATING TO 



MuscinesB. 



Dicranum and Dicranella.* — M. E. Heckel directs attention to 

 an abnormal organization in certain species of Dicranum, especially 

 D. scoparimn. 



The two genera Leucohryum and Sphagnum have in the leaves and 

 tegumentary tissue of the stem and branches perforated cells consti- 

 tuting a true capillary apparatus, through which the water of the 

 marshes where they grow spreads to the terminal parts ; differences of 

 degree only separating the organization of the two genera. 



Between the normal cell-structure of the great majority of mosses 

 and that of Sphagnum comes the structure peculiar to Dicranum. 



The leaves in this genus are formed of elongated cells, whose 

 thickened lateral walls, having from three to six readily recognizable 

 layers of cellulose, are attenuated at several (four to seven) places 

 through loss of substance, only the median layer of cellulose being 

 left intact. These attenuations resemble true canals at the points 

 where the external membrane is sufficiently thin. This cellular struc- 

 ture is only found in the leaves, insensibly giving place to the normal 

 structure at the points of their insertion on the stem. The other 

 species examined by M. Heckel also presented this arrangement, 

 the explanation of which is to be found in the rigidity of the leaves, 

 and the necessity for the penetration of water to the interior of the 

 hard tissue. 



None of the Dicranellce, except D. heteromalla, showed this structure, 

 a fact which, taken with others, leads the author to consider this 

 species to be a Dicranum. On the other hand the absence of the 

 structure in Dicranum crispum Hedw. supports the conclusion of 

 Lamy de Lachapelle that the latter is a Dicranella. 



The similarity which exists between the cells typical of Dicranum 

 and those figured by Solms-Laubach in the leaves of Libocedrus 

 Doniana and in the epidermis of the leaves of Biota orientalis shows 

 another point of connection between gymnosperms and cryptogams ; 

 and it is probable, M. Heckel says, that the areolated cells of conifers 

 are " only a deeper accentuation of the anatomical fact which is the 

 basis of this note." 



Development of the Sporogonium of Andresea and Sphagnum.t 

 — The following are the main results arrived at by M. Waldner in a 

 series of experiments carried on mainly to determine the answer to 

 Kuhn's question. Does the spore-layer of Andrecea owe its origin to 

 the basal square (Grrundquadrat), or to the layer of the wall ? 



I. As to Andrecea : — 



1. The number of segments formed by apical growth by means of 

 a two-edged apical cell varies between narrow limits, viz. from 

 11 to 13. 



2. The spore-layer originates in the third oldest segment, and to 

 this purpose are applied not more than three, or at most four, seg- 

 ments. The two oldest segments form, with the basal part of the 



* 'Comptes Rendus,' Ixxxix. (1879) p. 790. 

 t ' Bot. Zeit.,' xxxvii. (1879) p. 595. 



