713 



banchaceae and Monotropaceae, we need not be surprised at the 

 absence or slight development of cotyledons in the embryo. In the 

 exogenous Cuscutaceae, too, the species of which are wholly destitute 

 of leaves, the embryo is spiral, filiform, and perfectly acotyledonous. 

 Moreover, R. Brown evidently considers the Rafilesiacese and their 

 allies to be unquestionably related to the Aristolochiacese, which are 

 exogens ; although this great botanist is as evidently inclined to dis- 

 allow their claims to be looked upon as forming a distinct class. But 

 there are so many anomalies connected with their development and 

 mode of growth, and those anomalies seem all to point to the normal 

 mode of increase by means of a mycelium or thallus, observed in the 

 best understood fungoid members of the class of thallogens, that I 

 cannot but agree with Professor Lindley in believing that the rhi- 

 zogens do really form a distinct class, the several members of which 

 are as intimately related among themselves by numerous unmistake- 

 able peculiarities, as by these very peculiarities they are separated 

 from the other classes, and naturally located as a connecting link be- 

 tween the exogens and thallogens. 



In one part of his second paper on Rafflesia in the ' Linnean 

 Transactions,' Dr. Brown thus speaks of what has ever been a puz- 

 zling question in connexion with the economy of all entophytal para- 

 sites : — 



" I may here advert to one of the most difficult points in the eco- 

 nomy of Rafflesiacea3, namely, by what means their minute embryos, 

 which are at the same time of an extremely loose texture, are enabled 

 to penetrate through the bark of the plants on which they vegetate, 

 so as to account for such appearances as those exhibited in the nas- 

 cent Rafflesia Arnoldi represented in [its second stage], in which I 

 have been unable to trace any perceptible communication with the 

 surface, and where the parasite seems rather to grow out of than into 

 the stock."* 



Now it is this very circumstance which I look upon as affording 

 one of the strongest evidences of the fungoid nature of the organs of 

 vegetation among rhizogens. It is precisely in accordance with the 

 economy of entophytal thallogens, and equally opposed to all we 

 know of that of parasitical phaenogamous plants. By whatever 

 means the spores of entophytal fungi obtain access to the interior of 

 plants, we see nothing of the fungi until they are ready iojlower^ if I 



* I have described these figiu-es in connexion with Dr. Brown's remarks on the re- 

 ticulate base of Rafflesia (Phytol. ii. 714). 



