VIII. CHAEACEiE. 917 



kinds of reproductive organs, namely, macrospores in the outer fronds, and micro- 

 spores in the central fronds, 



The MACEOSroBES, to the number of 40 to 200 in each sporangium, are at first 

 united in fours, and later separate ; they are divided by a circular ridge into 2 hemi- 

 spheres, one of which is smooth, and the other, which is a little produced, is marked by 

 3 ridges, dividing its surface into 3 triangular spaces. The membrane of the macro- 

 spores is double ; the inner very thin and very smooth ; the outer thicker, crustaceous, 

 granulated, foveolate, or muricate, white or opaline. The macrospores open at 

 germination into 3 valves along the connivent ridges. 



The MiGHOSPORES, which resemble fine flour, are whitish when fresh, brownish 

 later ; there are above a million in each sporangium. They are at first united in 

 fours, then free, oblong, convex on the back, furrowed, furnished with a double mem- 

 brane like the macrospores, often granulated or papillose on the surface, and contain 

 a minute drop of oil. 



The development of the prothallus in Isoetes is absolutely the same as in 

 Selaginella, only the macrospores are developed in greater numbers in the sporangia, 

 and the archegonia are less abundant on the prothallus. The antherozoids are 

 somewhat similar to those of Ferns. 



ONLY GENUS. 

 Isoetes. 



Igoetece, regarded as a section oi Lycopodiacets by most botanists, and haying decided affinities with 

 them, seem to us nevertheless to form either a small family or a distinct tribe, whether we consider the 

 nature of their vegetative organs, or the structure of their sporangia and macrospores. 



The species of Isoetes are spread over the whole world. Some form a sort of close lawn, scarcely 

 more than an inch in height; while others, which live in deep water, often attain two feet in length 

 (/. Malinverniuna). 



VIII. CHARACEjE, L.-C. Richard. 



(Chares, Eiltz.) 



Acotyledonous plants, cellular, aquatic. Stems tubular, jointed, nahed or sur- 

 rounded hy several parallel elongated cells. Beakohes whorled on a level with the 

 joints. EEPBODUCTiyE organs formed of dntheridia and sjporangia, home on the 

 branches, and often accompanied by branchlets or bracteoles. Antheridia composed of 

 a spherical sac, containing oblong vesicles, whence spring numerous chambered tubes, 

 containing antherozoids. Sporangia oblong or ovoid, formed of spiral tubes, and 

 crowned by five protuberances (corOna), and containing a single starchy uni-embryonie 



Cha/racew are aquatic submerged vegetables, often exhaling a foetid alliaceous 

 odour, with transparent rhizome, composed of joints always formed of a single tube, 

 and fixed in the mud of stagnant and running water by tubular filiform very fine 

 colourless rootlets. The plant is sometimes reproduced by the lower nodes of the 



