8P0NGI0LES. 



[ 604 ] 



SPOHENDONEMA. 



of spongioles applied to the absorbing apices 

 of roots. So far is this from being a correct 

 account of the conditions, that, in reahty, 

 not only is the surface completely invested 

 with a continuous epidermis, but the grow- 

 ing point and principal absorbing surface is 

 found a little above the absolute extremity, 

 which is pushed forward by interstitial 

 growth. On the ends of many adventitious 

 roots (^^ e. roots which break out from the 

 interior of stems), especially remarkable in 

 the Duck-weed, exists a kind of cap formed 

 of tissue rather denser than that of the sub- 

 stance of the apex of the rootlet. This cap 

 either separates above, when the root breaks 

 out, and is then carried forward (like the 

 calyptra on a moss-capsule) as a distinctly 

 defined caj), called a pileorhiza, or the dense 

 layer at the end of the root loses itself gra- 

 dually upward in the epidermis of the sur- 

 face of the roots (fig. 684). Many young 



Fig. 684. 



Longitudinal section of the rootlet of an Orchis. 



C, C, Cellular tissue (camljium) in which ilevelopment 

 is still going on. F P, Fibro- vascular bundles gradually 

 becoming organized from above downward. 



Magnified 500 diameters. 



roots, especially such as grow in a moist 

 medium, are clothed with numerous radicle 

 hairs, which on superficial examination might 

 lead to the idea that the end was of S])ongy 

 character. The cells of the extremities of 

 the aerial roots of Orchids, &c., and of va- 

 rious water-plants, contain sufficient chloro- 

 phyll to give them a green colour. 



BiBL. Meyen, Pjianzenphysiologie, ii. 

 p. 1 ; Trecul, Ann. des Sc. nat. 3 ser. vi. 

 p. 303. 



SPORANGIUM and SPOROCARP.— 

 The term sporangium is applied to the 

 structure immediately enclosing the spores 

 of the Cryptogamia. The different forms 

 and conditions are describedunder the classes 

 of Flowerless plants. Sporocarp or spore- 

 fruit is the name given to the capsules or 

 similar organs which contain the sporanges 

 of tlie Marsileacese (see Pilularia). 



SPORENDONEMA, Desm.— A supposed 

 genus of Sepedoniacei (Hyphomycetous 

 Fungi). It is a very common occurrence in 

 autumn, to find the house-fly, dead,adhering to 

 walls, window-panes, &c., firmly fixed by its 

 proboscis, and with its legs spread out ; thus 

 differing from dead flies in general, which 

 have the legs contracted. In about twenty- 

 four hours after death, a kind of fleshy 

 substance, of a white colour, is found in the 

 form of a ring projecting out between each 

 of the rings of the abdomen, and in a day 

 or two after, the whole will be found dried, 

 and the surface of the wall or glass lightly 

 covered in a semicircle, at about 1-2 to 1" 

 from the fly's abdomen, with a cloud of 

 whitish powder. The whitish fleshy sub- 

 stance is found on examination to consist of 

 a vast number of short erect filaments grow- 

 ing out from the interior of the fly's body, 

 between the rings ; these filaments contain 

 large oil-globules, often arranged in a row ; 

 and their having been mistaken for spores 

 gave origin to the name Sjjorendonema, 

 applied to this fungus. Cohn has lately 

 described its growth somewhat minutely, 

 and changed the generic name to Empusn, 

 or rather Empusina, the first of these names 

 being already occupied. He correctly states 

 that the vertical filaments terminate in the 

 abdomen in a continuous, often branched 

 tube, and consists therefore of a single tubu- 

 lar cell. The upper free end, however, be- 

 comes cut off by a septum, and the terminal 

 cell acquires a campanulate form and a 

 darkish colour ; when ripe, it is thrown off 

 with elasticity, and a number of these 

 form the white cloud above mentioned. 

 Cohn endeavoured in vain to make them 

 germinate, and nothing like them Avas found 

 in the cavity of the abdomen of numerous 

 flies, in which the filaments were traced in 

 their earlier stages. From our own observa- 

 tions, we rather incline to regard them as 

 peridioles or spore-cases, com])arable per- 

 haps to that of Pilobohis ; or they may be 



