236 PHENOLOGY 



evaporation exceeds the precipitation in an enormous ratio but these 

 severe conditions bring into activity the spiny, succulent xerophytes. 

 These succulents are of two general types ; the one represented by the 

 cacti with storage stems and the other by the yuccas and agaves 

 with succulent leaves. Both of these types of plants bloom in great 

 profusion during the dry foresummer. 



C. The Humid Mid -summer.— This season begins about July 1st 

 and extends nearly to the end of September. The temperature is 

 exceedingly high but the greatest precipitation of the year is during 

 July and August. Millions of seedlings spring up when the rains 

 come and forty-eight hours may change the entire appearance of the 

 landscape. Some perennials, such as the great barrel cactus, bloom 

 at this time and there are many annuals among which are a number 

 of spurges (Euphorbia) and several parasitic dodders {Cuscuta) 

 which make a very rapid growth. 



D. The Dry After-summer.— The dry after-summer extends 

 through October and November which are rainless months. The 

 grasses which started late in the humid mid-summer ripen their seeds 

 and remain as dry tufts. Some other plants ripen their seeds during 

 the early part of this season but in general there is an almost total 

 cessation of vegetative activity. 



141. Phenology of the Pine-barren Region.— Harshberger has 

 studied the phenology of the pine-barren vegetation of New Jersey 

 and the information here presented is taken from his book which is 

 cited at the end of this chapter. His study included 548 pine-barren 

 plants which is only 7 less than the total number of native species 

 of the region. 



The period of activity of the pine-barren vegetation extends 

 through the seven months from the beginning of April to the end of 

 October, leaving five months when the vegetation is practically 

 dormant. There is very little activity in April, however, and in 

 fact the active period for the majority of the plants, so far as flower- 

 ing and fruiting is concerned, is in July, August and September, 

 the culmination being reached in August. The opening of the leaves 

 of the deciduous trees takes place largely in May and the leaves fall 

 in October. The period of photosynthetic activity of the mature 

 leaves is about four and a half months. The length of the flowering 

 period varies greatly with different plants, from fifteen days for some 

 trees, such as some of the willows and oaks, to one hundred and 

 fifteen days for the forget-me-not (Myosotis laxa) and one hundred 

 and thirty-five days for the water lily (Nymphoea variegata). Two 



