24 MM. Tulasne on the History of the Hypogceous Fungi. 



The veins composed of these filaments and the air interposed, owe 

 to this structure their dull white appearance, and opacity when 

 their tissue is examined in thin slices by transparent light, under 

 which circumstance they appear darker than the tissue rilled with 

 liquid forming the coloured veins. These aeriferous white veins 

 terminate at the external surface, either at a single point to which 

 all converge, or at several distinct points. 



In these plants, therefore, so shapeless and simple in appear- 

 ance, is formed a double system of veins, or rather of irregular 

 filamentous lamellae ; one set arising from the cortical tissue, 

 absorbing the surrounding moisture and serving to transmit this 

 humidity to the cells in which the spores are formed, being 

 therefore the organs of nutrition; the others, remarkable for 

 their white colour and opacity, terminating externally, intro- 

 ducing air into all parts of the Fungi and bringing it into con- 

 tact with the sporigenous cells themselves. This communication 

 of the external air with the internal lacuna? of the Fungus is 

 much more evident in the Truffles and in certain other Tube- 

 racece, than in the other hypogaeous Fungi, where the lacunae ana- 

 logous to those of the Truffles, although rilled with air, do not 

 appear to communicate with the exterior. 



The formation and structure of the spores have also been the 

 objects of very interesting researches by Messrs. Tulasne. In all 

 the true Tuberacece, the spores are developed freely in the cavi- 

 ties of the sporangia, or vesicular cells destined to produce them. 

 They are limited in number, and not very variable, in each of 

 these sporangia ; more than eight are never formed in one vesicle, 

 and in many species the maximum number is four. 



These spores exhibit very varied forms, according to the ge- 

 nera and species in which they are observed, but are perfectly 

 constant in the same species. This diversity however depends 

 almost solely upon the structure of the external membrane or 

 epispore, sometimes smooth, sometimes with points all over, or 

 variously reticulated. Beneath this external, coloured and rather 

 resisting membrane, is found a second integument, smooth, trans- 

 parent, more or less thick, but strongly resisting chemical agents, 

 and not only colourless in its natural state, but not coloured by the 

 action of iodine, and easily separable from the external integu- 

 ment by various reagents. The simple cavity of this internal 

 utricle of the spore is filled with oleaginous globules suspended 

 in a liquid which is probably albuminous, and is coloured yellow 

 or brown by iodine. 



These reproductive bodies, although less simple in their struc- 

 ture than has been sometimes supposed, are still far from repre- 

 senting on a small scale the organization of the Truffle itself, as 

 Turpin supposed ; their structure is not more complicated than 



