that he is "reluctant to distinguish N. ovata from [N. bongso] using this criterion only and [is] unable to suggest any other features that might serve this purpose". However, he retains N. ovata as a distinct species, noting that although the appendage may be present in N. bongso, this is rarely the case and even then it is usually less developed than in N. ovata. Nepenthes ovata is also similar to N. densiflora, with which it has been confused in the past. The two species can be reliably distinguished on the basis of the hook-shaped appendage, which is never present in N. densiflora. In addition, the lower pitchers of N. densiflora have an elongated neck that is far longer than the same structure in N. ovata. Furthermore, N. densiflora has differently shaped sepals in male and female flowers, whereas those of N. ovata are the same. In their description of N. ovata, Andreas Wistuba and Joachim Nerz compared the species to N. singalana. They noted that N. ovata differs in having an acuminate lamina apex, whereas N. singalana has a rounded apex. The two species also differ in the distribution of nectar glands on the underside of the lid. Nepenthes ovata has numerous glands near the midrib and is densely glandular near and on the hook-shaped appendage. In comparison, N. singalana is only sparsely glandular near the midrib and bears no glands near the lid apex. Nepenthes rigidifolia also bears some similarities to N. ovata, but can be distinguished on the basis of its thicker leaves, sub-apical tendril insertion, and mostly ovoid upper pitchers. In their description of the Sumatran species N. naga, the authors compared it to N. ovata. They distinguished it on the basis of its dichotomous lid appendage and frilled lid. Natural hybrids In the wild, N. ovata occurs sympatrically with a number of different Nepenthes species. At least five natural hybrids involving N. ovata has been recorded, four of which are found on Mount Pangulubao. Nepenthes ovata × N. spectabilis is known to occur along the summit trail of Mount Pangulubao. This hybrid produces pitchers roughly intermediate in appearance between its parent species. The peristome is flattened and expanded, but to a lesser degree than in N. ovata. The speckles of N. spectabilis are present, but the pitchers have a much lighter colouration. Most examples of this hybrid grow terrestrially and some climb into the forest