REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



composed of polygonal, tabular cells ; it is 

 lined by an inner layer, formed of the com- 

 mencements of the paraphyses and thecae, and 

 of the filaments with which they are con- 

 nected. The thecae are obovate cells, the 



Tliecas and paraphyses of Sphceria, about 300 diam. 



membrane of which is of extreme delicacy. 

 When fully formed, they contain from three to 

 eight oval spores, the epispores of which are 

 in the early condition delicate and pellucid, 

 but by degrees become brown and opaque. 



Fig. 147. 



Ripe spores of Cenangium Frangula, 350 diam. 



The contents of the spores, as is observed 

 throughout the higher Fungi, consist of a fluid 

 loaded with oily granules. The thecae are 

 arranged with their long axes perpendicular 

 to the inner surface of the perithecium from 

 which they spring, and are intermixed with a 

 greater or less number of slender, cylindrical 

 paraphyses. The whole perithecium is usually 

 enveloped in the filamentous stroma or my- 

 celium, from which it takes its origin. The 

 Discomycetes are represented by the Pezizae; 

 between these and the Sphceriae there are dif- 

 ferences of external form, which, though they 

 strike the superficial observer as important, 

 are in reality trivial. While the receptacle of 

 the Sphceria is a cyst with an apicial aperture, 

 that of the Peziza is a cup-shaped disc, the 

 concave surface of which looks upwards. This 

 surface is lined with an ascophorous mem- 

 brane, which resembles in every respect that 

 of a Sphceria. 



39. Along with the Pezizae and Sphceriae and 

 those allied genera which resemble them 

 in producing their spores enclosed in thecae, 

 there are other forms also included in the 



227 



Pyrenomycetes and Discomycetes, which , 

 while they resemble those last named in th e 

 general outline and structure of their recep- 

 tacles, differ from them completely in the 

 mode of origin of the spores. The simulta- 

 neous occurrence of some of these forms, 

 along with their ascophorous analogues, or, 

 in other instances, the successive develop- 

 ment of both kinds of receptacles in the 

 same position, had been frequently observed, 

 and had given rise in the minds of some my- 

 cologists to the suspicion of the existence of 

 a relation more close than was generally ad- 

 mitted. This suspicion did not, however, 

 take a sufficiently distinct form to lead to 

 observation until the MM. Tulasne, in a 

 series of researches scarcely completed, showed 

 that the genera in question, hitherto con- 

 sidered as distinct, were in fact identical, and 

 that receptacles containing thecae and para- 

 physes, are produced on the same stroma, or, 

 in other words, on the same individual plant, 

 as those which contain acrogenous spores. 



40. The earliest researches of MM. Tulasne* 

 were directed to the Pyrenomycetes. In some 

 species of Sphoeria, they found not only that 

 the same stroma produces receptacles with 

 acrogenous spores, which are followed by 

 others bearing thecas; but that, under cer- 

 tain circumstances, it may give rise to spore- 

 bearing organs, of a much simpler character; 

 viz. branching filamentous pedicles, bearing 

 at their terminations single spores, and rising 

 directly from the mycelium filaments, with 

 which the} 7 are continuous. In this condition 

 the plant cannot be distinguished from a 

 thread Fungus, and has been hitherto described 

 as such. 



41. The later observations of MM. Tulasne f 

 which are much more in detail, refer almost 

 entirely to Discomycetes. In a species of 

 Rhytisma, a genus of Discomycetes, which 

 inhabits the epidermis of the leaves of plants, 

 the stroma at first presents the appearance of 

 a black spot of various extent on the surface 

 of the leaf. In the substance of this stroma 

 the first receptacles are formed ; they are 

 cushion-shaped capsules, furnished with api- 

 cial apertures, like those of Sphoeria, and are 

 entirely occupied by a pulpy nucleus, which con- 

 sists of slender branched filaments, often so long 

 as to project considerably beyond the aperture. 

 These filaments bear at their extremities 

 innumerable minute linear sporules, which 

 are enveloped in an abundant mucilage, and 

 are expelled from the ripe capsules in the 

 form of a long cirrhus. After the capsules 

 which are developed during the early summer 

 months have discharged their contents, they 

 are succeeded by the lirelliform discs of the 

 perfect Rhytisma. These do not arrive at 

 maturity until the following spring, and bear 



* Notes sur 1'Appareil reproducteur clans lea 

 Lichens et les Champignons, Ann. des Sc. Nat. 3me. 

 S. t. xv. p. 370. 



t Nouvelles Recherches, &c. Comptes rentlus 

 Stance du 13 Dec. 1852. 



Q 2 



