MDMOLOGY ANiD ANALOGY 69 



to be in their form, are said to bd homologous with 

 bne another. On the other hand, Organs which are 

 morphologically different, but are adapted to the same 

 physiological function, at-e said to be analogous. 

 Thus the tubers of a potato are homologous with a 

 bfanch but analogous with a fleshy root like that of 

 a ranga-aloo, shank-aloo. Radish, &c., being reser- 

 voirs of food- materials. Similarly, the cladode of 

 Coccoloba platyclada is homologous with a stem but 

 analogous with a leaf, and the leaf-like thin green 

 cylindric grooved and jointed structures of jhau or 

 Beefwood [Casuarind) which have short sheaths of 

 connate scales at intervals are analogous with leaves 

 but homologous with branches. 



Trichomes is the name given to all epidermal 

 growths. Thus the hairs met with in young growing 

 roots, stems, leaves, &c. ; the bristles or stinging 

 hairs, as in jal-bichuti, lal-bichuti, and in pods of 

 alkushi; glandular hairs, as in lal-bharenda and 

 Drosera; scales (ramenta), as in Ferns; and prickles, 

 as in Rose, are all trichomes. Hairs vary much in 

 their form, length, number, fineness, and setting. 

 Thus a 'surface covered with soft scattered hairs is 

 said to be pilose; with long, scattered, stiff hairs, 

 hirsute; with short, stiff hairs, hispid; with close- 

 set, soft, short hairs, pubescent; and with long, soft, 

 interwoven hairs, tomentose. 



