Low nodded his head, gratified but not entirely convinced that she had fully estimated the magnitude of the endeavor. "I suppose," said Teresa, in the feminine postscriptum voice which it would seem entered even the philosophical calm of the aisles they were treading--"I suppose that _she_ places great value on them?" Low had indeed heard Science personified before, nor was it at all impossible that the singular woman walking by his side had also. He said "Yes;" but added, in mental reference to the Linnean Society of San Francisco, that "_they_ were rather particular about the rarer kinds." Content as Teresa had been to believe in Low's tender relations with some favored _one_ of her sex, this frank confession of a plural devotion staggered her. "They?" she repeated. "Yes," he continued calmly. "The Botanical Society I correspond with are more particular than the Government Survey." "Then you are doing this for a society?" demanded Teresa, with a stare. "Certainly. I'm making a collection and classification of specimens. I intend--but what are you looking at?" Teresa had suddenly turned away. Putting his hand lightly on her shoulder, the young man brought her face to face with him again. She was laughing. "I thought all the while it was for a girl," she said; "and"--But here the mere effort of speech sent her off into an audible and genuine outburst of laughter. It was the first time he had seen her even smile other than bitterly. Characteristically unconscious of any humor in her error, he remained unembarrassed. But he could not help noticing a change in the expression of her face, her voice, and even her intonation. It seemed as if that fit of laughter had loosed the last ties that bound her to a self-imposed character, had swept away the last barrier between her and her healthier nature, had dispossessed a painful unreality, and relieved the morbid tension of a purely nervous attitude. The change in her utterance and the resumption of her softer Spanish accent seemed to have come with her confidences, and Low took leave of her before their sylvan cabin with a comrade's heartiness, and a complete forgetfulness that her voice had ever irritated him.