某生物兴趣小组的同学在进行野外考察时，采回植物标本后拍摄了照片（如图所示），他们将肾蕨、葫芦藓和水绵分成一类，油松、向日葵和玉米分成一类．其分类依据是（　　）

____（用含α的代数式表示）．

可爱的猴子

    Look at those monkeys! How lovely they are! A mother and a baby are sitting on the hill. The mother is talking to its child. Some monkeys are jumping up and down. Others are swinging. I throw some bananas to them. One of them gets a banana. It runs away quickly and eats the banana behind the hill. I take photos of them. Suddenly I find two of them picking up stones. What do they want to do? Ha! They are talking photos, too.