SHAPES OF SEEDS 249 



placenta. The nature of the stalk differs to a certain 

 extent, in different species it is very short in the 

 Bean and very long in some species of Acacia, such 

 as the ACACIA DEALBATA and ACACIA MELANOXYLON 

 which have been introduced from Australia to some 

 of the mountains of South India. In RUELLIA, 

 ADHATODA, STROBILANTHES, and other genera of the 

 family ACANTHACE^E, the stalks become very hard 

 .and when the pod opens, spring up elastically and 

 jerk the seeds out. But in most cases the stalk is 

 just the connecting link between the ovule and the 

 placenta, and after the seed has matured is of no 

 particular importance at all. 



The hilum, we have already learnt, is the scar 

 left on the seed when it was attached to the stalk. 



Only in a very few species does the ovule develop 

 straight, so that the seed stands straight out from 

 the placenta. When it does so, it is called ortho or 

 Straight, and we find such seeds in ANTIGONON and 

 others of the family POLYGONACEvE. 



In most cases the ovule as it grows becomes bent 

 back on its stalk so that the further end (where the 

 micropyle is) comes to be nearest to the placenta. 

 It is then said to be anatropous. Such seeds occur 

 in the greater number of families instances are the 

 GERANIACE.E (Balsams) the EUPHORBIACE^: (Castors) 

 the Orchids and the Lilies. 



Sometimes the ovule becomes not only bent back 

 on its stalk, but curved also as in the bean, gram 

 and all leguminous plants, in HIBISCUS and other 

 MALVACEAE, in CHENOPODIUM and in the AMARAN- 



It is then termed campylotropous and is 



