120 



FRANCIS E. LLOYD 



from the soil. The temperature gradient from the soil upwards 

 on a typical high-fog day is indicated in table 3. 



Without assuming that the temperatures found on this day 

 were the absolute favorable ones, it may be argued that the 

 temperature differences as between positions 5 cm. and, at most, 

 20 cm. are sufficient to cause the seeding and non-seeding of the 

 plant, and this difference lies within five degrees at the most. 

 In 1915 a plant was prostrated, and lay on a grassy and there- 

 fore cooler surface, and another w^as purposely so placed. Flowers 

 were formed, but no fruit. 



It is therefore concluded that if the prevailing day tempera- 



tures at Carmel, California, which are low enough to prevent 

 reproduction by seed, were five degrees higher, during the warm- 

 est hours, reproduction by seed would take place at least in 

 sufficient measure to enable the species to persist.^ The tem- 

 peratures which permit vegetative activities are not identical 

 with, but are lower than those more intimately connected with 

 reproduction. The more delicate physiological responses shown 

 in anthesis and dependent processes are probably responsible 

 for the frequently observed peculiarities of flowering in many 

 of the higher plants, e.g., the cacti.'* In the instance before us 

 an illustration is afforded of the possible effect of slightly in- 

 adequate temperatures on distribution by inhibiting reproduction. 



^ Seeds germinate and seedlings develop well in the situation in which flower- 

 ing and seed-development do not take place. 



'' F. E. Lloyd: Observations on the Flowerine Periods of certain Cacti. Plant 

 World 10: 31-39. 1907. 



