32 



ERICACEAE 



Fig. 293. Aectostaphtlos nummula- 

 RIA Gray. Colony on the south slopes of 

 Mt. Tamalpais ; a cluster of shrubs on the 

 margin of a fire band, completely killed by 

 the intense heat but not strueturallv in- 

 jured. Sept., 1913. 



Field experience with the genus Arctostaphylos began with the author as a lad during the 

 years 1883 to 1889 in the Vaca Mountains, the southernmost block of the inner North Coast Range 

 facing the lower Sacramento Valley. Observing the chaparral he noticed that one species made a 

 low bush l! or 3 feet high with several small stems arising from the ground, the stems in fact borne 



on a basal woody block and rightly interpreted as 

 stump-sproufcs. This species was common in the chap- 

 arral formation of the main ridge, a region fire- 

 harried at intervals for centuries. It was, indeed, 

 static in its area notwithstanding fire and was re- 

 markable in that it displayed many rigid stems from 

 an enlarged woody base which evidently developed 

 new shoots after each successive conflagration. It 

 was spoken of as Arctcstaphylos tomentosa, a blan- 

 ket name of that time, though the shrub was in real- 

 ity a distinct species, A. glandulosa Eastw., a name 

 not then published. Another species, a large shrub 

 5 to 8 feet high, with a single trunk at the ground, 

 was rare in the range. The effect of chaparral fires 

 upon it was lethal. It did not stump-sprout. This 

 shrub passed as Arctostaphylos pungens and was 

 later properly published as a distinct species under 

 the name A. manzanita Parry. Eeoccupation by this 

 species, a vanishing one in the Vaca Mts., was lim- 

 ited, because the area lies climatically beyond the 

 present margin of its optimum requirements. 



Follo\\'ing these juvenile experiences, systematic 

 field work was in the course of time extended widely 

 over California. In the region of San Francisco Bay, 

 one admirable area, the slopes of Mt. Tamalpais, 

 furnished a striking contrast, as to fire relations, between two Arctostaphyli, namely Arctostaphy- 

 los glandulosa (at that time passing as A. tomentosa) with its remarkable root-crown sprouts aris- 

 ing from a broad woody platform, and Arctostaphylos nummularia, the shrubs of which are killed 

 completely by fire. At long intervals, after great chaparral fires on Mt. Tamalpais, the spectacular 

 differences between these two species was used for demonstration to groups of students as an inci- 

 dental part of regular field practice on vegetative and seed reproduction in a natural woody cover. 

 Occasionally a promising student, trained to study the chaparral, was directed to watch for marked 

 examples of reaction of native shrubs to fire. With such aid the field of observation became even 

 more extended. Charlotte M. Hoak made pertinent observations in Mendocino County in the year 

 1914. F. B. Herbert and A. E. Wieslander completed in 1914 an excellent report on the woody 

 cover of the Muir Woods watershed and confirmed reactions to fire in the case of many species. 

 Both of these students extended their observations elsewhere up and down the state in later years. 

 At about the same time W. C. Mathews made useful oral reports of fire reactions in the San Fran- 

 cisco Bay region and on the Mendocino coast. Leland S. Smith and other students developed inter- 

 est in the same subject. Accumulation of evidence was slow and often involved in difficulties, but 

 it was important, because recognition of differences in reaction to fire furnished factual matter of 

 decisive value in the validation of necessary segregation of our species, most of which in former 

 times passed en bloc under two names, Arctostaphylos pungens and Arctostaphylos tomentosa. 

 Generalizations were cautiously made and observations withheld from expression because of the 

 uncertainty of species definitions in this genus. While much valuable information has now been 

 placed on record, even so, knowledge of the biology of our Arctostaphyli is still insufficient. 



The earlier accounts of Arctostaphylos species in the literature are taxouomieally formal and 

 derived in the main if not wholly from herbarium specimens. Neither Gray, Parry, Greene, Howell 

 nor any other author of their time mention root-crown sprouting or reaction to fire. Indeed no 

 description of a species includes mention of this subject until the year 1916. In that year the 

 author published an article (prepared two to three years previously) putting on record the differ- 

 ences in reaction to fire of various species of Arctostaphyli (Eegeneration in Manzanita, Madrono 

 1:3-11, figs. 1-5, — 1916). The textual matter was supplemented by figures illustrating response 

 to fire, root-crown sprouting on the one hand and lethal effects of fire on the other in the case of 

 certain species. This phase of the study of Arctostaphylos was amplified in the author's "Revision 

 of the California Species of the genus Arctostaphylos" (Madrono 1:76-96, figs. 1-3, — 1922), and 

 was summarized in a stUl later paper, "The Role of Fire in the Chaparral," delivered before the 

 Fifth International Botanical Congress at Cambridge, England, in 1930 (Fifth Intern. Bot. Cong. 

 Rep. Proc. 114-116,— 1931). 



Determination of reaction to fire is important because, as has been shown, the species are 

 only weakly or inconstantly separated by ordinary morphological marks. The hue of the leaves 

 may be a valuable point and sometimes gives a better means of identification than the shape. The 

 nature of the bark on the main trunk in certain species affords a character. The fruits are to a 

 great degree alike but may differ in minor details, though sometimes developing an indicative 



