Dhammanussati means Recollection of the Dharma.

Even though the Buddha in his physical form is no more with us now, we still have the Dharma as our guide and teacher. Thus the Dharma has virtually taken the place of the Buddha. In fact, the Dharma itself constitutes Buddhahood and Buddhahood is, in truth, nothing but the Dharma.

Buddhahood is achieved through the realization of the Dharma and there could never have been a Buddha without the Dharma. That is why the Buddha says:
"He who sees the Dharma sees me, and he who sees me sees the Dharma."

Obviously, "me" here doest not signify the Buddha in his physical form, as generally understood, but the Buddhahood on Buddha-nature with which the Dharma is equated. Thus in the ultimate sense both the Buddha and the Dharma are one and the same.

Like Buddhanussati, Dhammanussati is also recited as a means of concentration meditation practice. The following is the passage under discussion:

Well-expounded is the Dharma by the Blessed One,
To be realized by oneself,
With immediate result,
(Is) capable of standing the test,
Leading to Nirvana,
To be attained by the wise,
Each for himself.

It is clear from the above passage that the Dharma is something to be practiced, not merely studied or memorized. To practice Dharma means to follow the teachings of the Buddha and to come closer to Buddha-nature. Remember that the Dharma will benefit us only when we seriously practice it.