PTERIDE^E. 



[ 644 ] 



PTEROPTUS. 



Adiantvm. Sori marginal, linear or glo- 

 bose, numerous and distinct, or confluent. 

 Indusium shaped liked the sorus, formed of 

 the reflexed margin of the fronds, with the 

 capsules beneath. 



Ochropteris. Sori marginal, transversely 

 oblong, at the apices of the lobes of the 

 segments. Indusium the same shape as the 

 frond, formed of its reflexed margin. 



Lonchitis. Sori marginal, in the sinuses of 

 the frond, reniform or elongated. Jndusium 

 shaped like the sorus, membranous, formed 

 of the frond. 



Hypolepis. Sori marginal, in the sinuses 

 of the frond, small, subglobose, uniform. 

 Indusium formed of the reflexed margin, 

 membranous. 



Cheilanthes. Sori terminal or nearly so on 

 the veins, at first small, subglobose, after- 

 wards confluent. Indusium formed from 

 the changed reflexed margin, roundish, or 

 confluent, not quite continuous. 



Cassebeera. Sori terminal on the veins, 

 globose or oblong, not reaching beyond the 

 branches of a single vein. Indusium in- 

 serted within the margin, and separate from 

 it, shaped like the sorus. 



Onychium. Sori on a continuous linear 

 receptacle, connecting the apices of several 

 veins. Indusium parallel with the margin 

 of the segments, linear, opposite, pressed 

 over the sori, the edge nearly or quite 

 reaching the midrib. 



Llavea. Sori linear, occupying the 

 whole length of the changed pod-like seg- 

 ments of the upper part of the frond. In- 

 dusium the same shape, rolled over and 

 concealing them. 



Cryptogramma. Sterile and fertile fronds 

 usually different, from the same root ; sori 

 terminal on the veins, at first subglobo.e, then 

 confluent, the continuous indusium formed 

 of the changed inrolled margin of the frond. 



Pellcea. Sori intramarginal, terminal on 

 the veins, at first dot-like or decurrent on 

 the veins, then running into a line. Indu- 

 sium formed of the more or less changed 

 edge of the frond, continuous, sometimes 

 very narrow. 



Pteris. Sori marginal, linear, continuous, 

 occupying a slender filiform receptacle in 

 the axis of the indusium. Indusium the 

 shape of the sorus, usually membranous, at 

 first covering it, then spreading. 



Ceratopteris. Sori placed on two or three 

 veins which run longitudinally down the 

 frond, and which are nearly parallel with 

 both the edge and the midrib. Indu- 



sium formed of the reflexed margin of the 

 frond, those of the two sides meeting at the 

 midrib. 



Lomaria. Sori linear, continuous, lon- 

 gitudinal, and occupying the space between 

 the midrib and the edge. Indusium mem- 

 branous, formed of the revolute margin of 

 the frond. 



PTERIS, Linn. A genus of Pteridese 

 (Polypodiaceous Ferns), represented by one 

 indigenous species, Pteris aqidlina, the com- 

 mon Brake Fern ; numerous tropical species. 

 (Hooker, Syn. 153.) 



Fig. 612. 



Pteris. 



A pinnule with marginal indusiate sori. 

 Magnified 10 diameters. 



PTEROCOM'MA, Buckt A genus of 

 Aphidse. P. pilosa, on willow-twigs. (Buck- 

 ton, Aphides, Ray Soc. ii. 142.) 



PTERODI'NA, Ehr. A genus of Rota- 

 toria, of the family Brachionaea. 



Char. Eyes two, frontal; foot simply 

 styliform. At the end of the tail-like foot 

 is a suctorial disk; jaws with the teeth 

 either arranged in a row, or two teeth only 

 in each. 



Three species; two freshwater, one 

 marine. 



P. patina (PI. 44. fig. 20). Testula mem- 

 branous, orbicular, crystalline, roughish 

 near the broad margin ; a depression pre- 

 sent between the rotatory lobes. Fresh- 

 water; length 1-120". 



BIBL. Ehrenberg, Infus. 516 ; Pritchard, 

 Inf. 711. 



PTEROP'TUS, Dufour. A genus of 

 Acarina (Arachnida), family Gamasea. 



Char. Body depressed ; last joint of palpi 

 longest; legs stout, with short joints. 



P. vespertilionis (PI. 6. fig. 39). Found 



