ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 89 



surrounded by eight (occasionally seven) very systematically arranged 

 guard-cells, and each stomate opens into a well-developed air-chuinber. 

 The peculiar oil-bodies of the Hepaticaa are scattered throughout the 

 thallus, ventral scales, and sporogonial receptacle. It is monoecious, 

 and the autherids form a single row just behind the sporogonial re- 

 ceptacle. The archegones are formed, in two rows of usually three or 

 four each, just behind the apical cell. After fertilisation, the oosphere 

 enlarges to nearly double its original size ; the first and second division- 

 walls are respectively transverse and longitudinal. In the development 

 of the sporogone the spore-mother-cells and elater-mother-cells are 

 readily distinguished ; the former are nearly spherical, the latter 

 elongated ; and the nuclei of the latter are much smaller than thi.se of 

 the former. 



Algae. 



Pyrenoids of Algae.* — Dr. A. M. Boubier has studied these struc- 

 tures in the genera Stigeoclonium, Spirogyra, Mougeotia, and Chsetopliora. 

 Each pyrenoid is invested by a protoplasmic membrane, perfectly 

 differentiated aud independent of the chromatophore, at least when 

 mature. The membrane encloses a leucoplast, the centre being occupied 

 by a crystalloid substance. In Spirogyra and in Mougeotia scalaris, a 

 number of pyrenoid-structures are connected together, by a membrane 

 which the author terms a pyrenodesm, into a compound pyrenoid, con- 

 taining in its centre a pyrenocrystal. By fixing in absolute alcohol and 

 then examining in Millon's reagent, the chromatophore is nearly or 

 completely destroyed, exposing the pyrenoid ; the crystalloid is sur- 

 rounded by a hyaline zone formed by the dissolution of the starch. 



Holdfasts of the Floridese.f — Carrie M. Derick describes the hold- 

 fasts (hapters) in a number of genera of Floridese, chiefly belonging to 

 the Khodymeniales. 



The species examined of Rhabdonia, Lomentaria, and Champia, all 

 agree in passing through a segmentation stage, resulting in a somewhat 

 spherical mass of cells ; in the elongation of four basal cells ; and in 

 the subsequent development of four primary rhizoids, which biauch 

 repeatedly, and finally form a large discoid holdfast composed of pseudo- 

 pareuchymatous tissue. 



A different development occurs in the Rhodomelaceaa as exhibited 

 by Chondria tenuissima, Polysiphonia violacea, and Dasya elegans. 

 These three species agree in forming a primary root-cell which elon- 

 gates into a rhizoid terminating in a clasping disc, and in developing 

 secondary rhizoids, which are sent out by the root-cell, the cell adjacent 

 to it, and the cortical cells at the base of the frond. But, while the 

 rhizoids of Polysiphonia are unicellular, unbranched, and free, those of 

 Dasya and Chondria are multicellular, branched, and aggregated iuto 

 a compact cell-mass, which in section resembles parenchymatous tissue. 



Among the Ceramiaceae examined the species differ greatly both in 

 the manner of development and in the form of the holdfast, agreeing 

 only in the production of one primary root-cell. Spermothamuion 

 Turneri forms short unicellular rhizoids with terminal discs and no 



* Bull. Herb. Boissier, vii. (1899) pp. 451-8, 554-9 (26 figs.). 

 t Bot. Gazette, xxviii. (1S99) pp. 246-63 (3 pis. and 5 figs.). 



