PHYSIOLOGY AND MORPHOLOGY OF CALIFORNIA HEPATIC^ 35 



notably an Italian form in which he observed entire portions of 

 the thallus developed into tuber-like structures. Stephani ^ has 

 also described similar structures for Riccia bulbifcra. None of 

 our Californian Riccias has yet been described as bearing 

 tubers or tuber-like growths, though Riccia trichocarpa, men- 

 tioned elsewhere in this paper, is well adapted to withstand 

 severe exposure, the thallus being densely clothed with tawny 

 setae .3 to .65 mm. long, with those toward the apex in as many 

 as eight to twelve series, affording a very effective protection 

 against excessive drying. Though these tuber-like structures 

 wherever they have been examined are always found to con- 

 tain large quantities of reserve food, there is little doubt that 

 they are instrumental as water-storage organs. 



STUDIES IN THE GERMINATION OF SPORES. 



In a previous paper the writer has described and figured the 

 germination of the spores of Fossombronia loiigiseta. The 

 results of experiments then carried out showed the early devel- 

 opment of this species to agree closely with certain forms, not- 

 ably SphcBTOcarpiis cali/ornicns, investigated by Campbell.^ 



Most of the hepaticas of this region produce spores character- 

 ized by a heavy, more or less sculptured exosporium which 

 Leitgeb^ found to consist of two parts or layers of which the 

 inner belongs to the spore itself and is the exine, while the 

 perinium or outer layer is formed later and consists of parts of 

 the sporocyte. Leitgeb suggests the probability of the perinium 

 as a protection against drought but in the light of more recent 

 studies of certain forms producing thick-walled spores, e. g.y 

 Corsinia, Preissia^ Anthoceros and SfhcBvocarpus^ it may be held 

 that the perinium can certainly have nothimg to do with a rest- 

 ing period, for spores of these forms germinate readily within a 

 few days after being sown. As to the thick exosporium fur- 

 nishing a protection against excessive dryness there can be little 

 doubt, although such forms as Corsinia and the aquatic Ric- 



' Stephani, 1S9S : Species Hepaticarum. Bull, de I'Herb. Boiss., Vol. VI, p. 



333- 



''■ Campbell, 1S96 : Notes on Sphserocarpus. Enthea, Vol. IV, No. 5, PI. 2. 

 * Leitgeb, 18S4, Ueber Bau und Entwicklung der Sporenhaute, Graz. 



