Acclimatization in Arizona. 19 



larger plants, these species suffer noticeably during our hot 

 summers, and not uncommonly they die out completely. With 

 partial shade they get through the summer fairly well, after which 

 they make a moderate growth for the remainder of the season. 

 Only rarely, however, do they appear as robust here as in the 

 northern states. 



With several trials in various parts of the territory where 

 high summer temperatures prevail, paeonia plants have never 

 blossomed and have generally failed to endure for a single year. 

 Golden-glow and columbine are strictly summer growing species 

 notwithstanding our mild winter climate, native forms of both 

 occurring in our mountains at elevations of 7,000 to 8,000 feet. 

 On the University grounds at Tucson these plants do fairly well 

 during the spring and fall seasons, while in the hot period, June 

 to September inclusive, their leaves scorch badly. Both are 

 showy flowers at Flagstaff, Arizona, where the summer temper- 

 atures are comparatively cool. Common tansy, rosemary or 

 costmint, and bouncing bet fail at the lower altitudes with ex- 

 treme summer heat, and succeed well in the cooler sections at 

 higher altitudes. 



The behavior of gladiolus is especially interesting. At 

 Tucson this plant starts growth with the warm days of early 

 March. Except with some protection, however, it seldom gets 

 into flower before it is cut down by the extreme heat of June, 

 the plants wilting badly and scorching, notwithstanding frequent 

 watering. Under these conditions the bulbs do not mature 

 fully and often decay in the ground before being dug. Of 100 

 bulbs set out by the writer in March 1907, only twelve grew 

 the second season, and a number of these died the following 

 year. Among those that survived the ordeal, for such it was, 

 one has shown notable resistance to heat, blossoming well and 

 making a robust growth each season with heavier than ordinary 

 irrigation. It is quite possible that a strain of gladiolus plants 

 better suited to this climate could be developed from a plant 

 like this. 



The early spring bloomers, namely, tulips and bleeding 

 heart (Dicenira), also should be mentioned here. Under any 

 conditions the growth of these plants is well out of the way be- 

 fore the hot weather sets in, so that this could have no effect on 

 them. The interval of cool spring weather in our climate be- 



