1916] Gilkey: A Revision of the Tuherales of California 285 



the simple cavity of tlie ascoearp becomes filled with folds of tissue, 

 it is dissected into canals of various form. These are first represented 

 in Geopora, and continue throug:h the line. These canals are generally 

 lined with a palisade of asci and paraphyses, some of the latter at 

 times developing into the canals and filling them \nth a mass of 

 branched and tangled hyphae. Such canals are called venae externae 

 and are seen in Pseudohalsaniia, Stcphcnsia, Pachyphlocus, Tiiher, 

 and Piersonia. In other cases the paraphyses all remain as palisade 

 or are absent, and the ]>assages are left free, as in Geopora and Jlijd- 

 notrya. 



As the ascoearp becomes more and more crowcU'd with minute, 

 irregular folds of tissue, these are fitted together until the hymenium 

 loses all indication of order; and the asci are massed in apparently 

 irregular form in areas separated by narrow veins, the latter repre- 

 senting the original folds or projections which were large enough to 

 retain their identity. This is the condition found in Tuber. In Pier- 

 sonia the internal folding has not been so great, but the hymenial 

 areas are distinct, through the loss of asci for long distances upon the 

 venae externae, and the consequent shrinkage of the latter, forming 

 narrow canals. 



Line B branches from the original with the definite appearance in 

 Balsamia of closed chambers. These are first to be considered in 

 Geopora, in which various folds coalesce, closing the passages. These 

 chambers become complicated in Hydnotryopsis by infolding of their 

 walls, producing a condition in each chamber similar to that of the 

 original cavity of Geopora. In (Jhoiromyces the open canals of Hydno- 

 tryopsis become filled with hyphae formed by development of para- 

 physes; and finally in Terfezia and Delastria all semblance of ovdw 

 in the hymenium is lost, as in Tuber. 



These lines which were arranged merely upon ascoearp structure, 

 were found to exhibit development in spore characters and numbers 

 as well. For example, Hydnocystis has spores which are entirely 

 smooth, and tliis character continues through the genera to Pachy- 

 phlocus of the one line and Iliidiiotryopsis of the other. In tlic off- 

 shoot Genea, however, sculptured spores are observed. The asci of 

 all genera to Tuber and Delastria contain generally eight spores, from 

 this point the number varying through one to four. 



Several points of the preceding theoretical line of development of 

 the Tuberales have been borne out to some extent in a study of these 

 plants. (1) In Geopora HarJinessii every stage was found between 



