238 THE PHYSIOLOGY OF PLANTS 



watering until the fruits have attained about one-half of their 

 normal size, and until the sclerenchymatous cells which form 

 the stone are sufficiently developed. During the period in 

 which the stone is formed the fruit doeS not increase much in 

 size, which seems to indicate that the fruit does not during 

 that time require so much water. It is just at this period 

 that the fruits drop if the plants are copiously watered. One 

 should also guard against beginning watering too suddenly in 

 case the trees have been passing through a considerable period 

 of drought, which may have prematurely coloured the fruit. 

 A sudden and copious supply of water may cause a total fall 

 of the fruits ; the water supply has to be begun gradually, so 

 as to get the tree used to the more active transpiration which 

 this necessitates. 



We may here add, that the usual treatment of plants 

 which have been suffering from drought is a wrong one; as 

 a rule, they are copiously watered, shaded, and, where it is pos- 

 sible, they are placed in a saturated atmosphere. One forgets 

 that the plant has become unaccustomed during the period 

 of drought to any great transpiration, and this must gradually 

 increase before the water can be properly absorbed. The 

 transpiration can, however, be increased by placing the plant 

 after the first watering in a light place and in a dry atmosphere. 

 We can easily detect in a plant placed on a balance that the 

 amount of transpiration gradually increases and the plant will 

 recover, whereas a plant suddenly swamped with water and 

 placed in a dark damp place will recover very slowly indeed, 

 or may die altogether. 



§ 46. What are the conditions governing the production of seeds ? 



The ovules become changed by the act of fertilisation, i.e., after 

 the contact of the pollen tube with the egg-cell, and develop 

 into seeds. Without fertilisation no seeds are ever developed ; 

 but a fruit, especially a pseudo-carp, formed by a succulent 

 axis, may develop without any fertilisation having taken place. 

 Thus pears may become fully formed by abnormal development, 

 and will be found to be without a core, but edible. 



