ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1001 



sporogomum, formed by apical growth, consists of only from six to eight 

 segments, and the sporogenous layer does not spring from the basal 

 but from the parietal layer, the uppermost three layers and the apical 

 cell take part in its formation. 



Hygroscopic Movements of the Thallus of Marchantiese.* — Dr. O. 



Mattirolo finds the thallus of certain Marchantiese to be remarkably 

 sensitive to hygroscopic influences. The observations were made 

 chiefly on species belonging to the genera Plagiochasma, Behoulia, 

 Grimaldia, Fimhriaria, and Targionia. 



Taking Grimaldia dichotoma as an example, the flat thallus consists 

 of three distinct layers of tissue, viz. (1) the epidermal layer, perforated 

 vi^ith stomata ; (2) the assimilating layer, consisting of rows of chloro- 

 phyllous cells at right angles to the surface, between which are large 

 air-chambers ; and (3) the mechanical layer, composed of closely-packed 

 sj)herical or polyhedral cells without intercellular spaces, containing a 

 certain amount of chlorophyll, starch-grains, and oily substances. The 

 whole is attached to the soil by rhizoids, and its under surface covered 

 with brown or dark violet scales. 



The seat of the movements is in the mechanical layer, the cells of 

 which are remarkably hygroscopic, more than doubling in size on 

 absorption of water. To such an extent does the thallus shrink up on 

 desiccation that it seems almost to disappear ; but it has the power of 

 retaining its vitality in this condition for a very long period (certainly 

 as much as thirteen months), swelling and resuming its normal appear- 

 ance when again moistened. The movements are entirely independent 

 of light or darkness, and are produced solely by changes in the moisture 

 of the air. When the air is dry, the thallus folds itself up, the free 

 margins rising and bending over, so that the ventral scaly surface com- 

 pletely covers the whole thallus, concealing the stomata, and protecting 

 it from further desiccation and from injury from changes of temperature. 



The cells of the mechanical layer were very frequently found to be 

 occupied by Nostoc colonies. 



Characese. ' 



New Chara-t — Dr. 0. Nordstedt describes a new species of CTiara 

 from Australia, belonging to the section Euchara. Its diagnosis he gives 

 tbus : — Ch. haplostephana, hisfi/pulata, haplostiche, corticata, gymnophylla, 

 dioica. The leaves are in whorls of from 7 to 10, with 2 to 4 antheridia 

 in the secondary whorls of the male plant ; the diameter of the stem is 

 from 0-2 to O'i mm. ; the leaves 0-15, the secondary leaves 0*12 mm. ; 

 the antheridia 0-45 to 0-60 mm. ; the nucleus of the sporangium black, 

 with seven spirals, from 0-42 to 0'52 mm. long and 0'30 to 0*35 mm. 

 broad. 



New Nitella-I — Dr. 0. Nordstedt describes a remarkable new species 

 of Nitella, which he calls N. dualis, obtained from Liberia among the 

 results of the " Gazelle " Expedition, It has unusually long slender 

 internodes, and the secondary and tertiary branches are densely clustered, 

 so as to give it a very beautiful appearance. 



* Malpighia, ii. (1888) pp. 181-223 (2 pis.). 



t Hedwigia, xxvii. (1888) p. 189 (1 pi.). 



X Forschungsreise S.M.S. Gazelle, part iv. [Bot.], Characese, 2 pp. and 1 pi. 



