Ushadi There is a famous doctrine in Biology which all of us are familiar with "Ontogeny Repeats Phyllogeny". The modified leaf of Australian Acacia (Acacia auriculiformis) is derived from the normal bipinnate leaves so common in other Acacia species. In this evolutionary modification the pinnae got reduced and their function was taken up by the flattened petiole (called Phyllode, as against phylloclade of Opuntia which is a modified stem taking function of leaf) of the leaf in the adult plant. Hence it is common to see juvenile plants with some pinnae at the tip of the phyllode, and these eventually fall off. Adult trees are without these pinnae and have only flattened phyllodes functioning as leaves. Of course every leaf has to fall once it has become old: In evergreen trees they develop and fall off periodically so that tree remains green throughout the year (Mango, Alstonia, etc.); In deciduous trees on the other hand the fresh leaves appear in spring (Late February-March-early April) and all fall off in autumn so that tree remains naked for few months in winter (Prunus, Pyrus, Salix, Populus). Delhi (and perhaps some other warmer cities in India) don't have typical four seasons. Here so called autumn is brief few days in March when deciduous trees suddenly lose their leaves and fresh leaves come up after a gap of few days, the Delhi Spring.
I hope I have shared some helpful information. -- Dr. Gurcharan Singh Retired Associate Professor SGTB Khalsa College, University of Delhi, Delhi-110007 Res: 932 Anand Kunj, Vikas Puri, New Delhi-110018. Phone: 011-25518297 Mob: 9810359089 http://www.gurcharanfamily.com/ http://people.du.ac.in/~singhg45/ On Fri, Mar 23, 2012 at 10:44 AM, shrikant ingalhalikar < [email protected]> wrote: > Dear Usha di, > > Wish you a happy Hindu New Year. Thank you very much for your curiosities, > hope I satisfy them at least partially. > > This is my first attempt to handle the new format yet I believe that my > post carries the name Acacia auriculiformis. Ironically the post itself > became more intriguing than the leaves. Earleaf Acacia and Australian > Acacia are more names to help you navigate with Google. Pardon me for > defficient and confusing information. I am attaching another image to help > you ID this invasive tree that has reached most of our wild habitats. > > I am also a pitiable non botanist like most of us. Please excuse me to > have narrated in a style that disguises me to be a card carrying botanist. > I take privilege of passing the batton of your queries to a person who > carries the necessary stars and shoulder pips.With regards.Shrikant > > > > > > > On Thursday, March 22, 2012 10:02:53 PM UTC+5:30, Ushadi wrote: > >> BUT I am still ignorant of the tree's ID and >> what happens when that flat "leaf " falls off, does it mean that the >> small leaves on its apex fall off too? >> so some leaves have pinnae and some donot? as in this pic... >> >> if I knew the name , I could google it... >> then I would not have to bother you... >> >> but all this discussion without a name, assumes that most of the 1900 >> members are all botanists... REMEMBER ONLY A HANDFUL ARE CARD CARRYING >> BOTANISTS>> THE REST OF US are NON BOTANISTS.... so please take pity on >> us .... >> >> thanks >> Usha di >> ==== >> >> >> >> On Thu, Mar 22, 2012 at 8:30 PM, Satish Phadke <[email protected]>wrote: >> >>> Very good illustration. >>> >>> On Thu, Mar 22, 2012 at 7:20 PM, shrikant ingalhalikar < >>> [email protected]> wrote: >>> >>>> This common exotic tree is seen with only falcategreen veinless >>>> phyllodes whichdisguise like simple leaves. Like most Acacias this should >>>> havebeen havingbi-pinnate leaves. Interestingly this Acacia too has >>>> bipinnate leaves but they are seen only in sapling stage. Pinnae2, 2-5 cm, >>>> deciduous; leafletsopposite, 6-10, sessile, oblong, 5-8 mm; petiole 5-8 mm, >>>> modifying and elongating to a phyllode 10-15 cm long. Scar of fallen pinnae >>>> can be seen at the rounded apex of the phyllode. Regards, Shrikant >>>> Ingalhalikar >>>> >>> >>> >>> >>> -- >>> Dr Satish Phadke >>> >> >> >> >> -- >> Usha di >> =========== >> >> -- Dr. Gurcharan Singh Retired Associate Professor SGTB Khalsa College, University of Delhi, Delhi-110007 Res: 932 Anand Kunj, Vikas Puri, New Delhi-110018. Phone: 011-25518297 Mob: 9810359089 http://www.gurcharanfamily.com/ http://people.du.ac.in/~singhg45/
