95 



Fig. 125 (PI. XIV). The venation of the lateral lobes of the leaves 

 is dichotomous. The epidermal cells show the usual sinuous out- 

 lines, but there is a marked difference between the upper and 

 the lower epidermis. The cells in the former case contain little 

 or no chlorophyll and no stomata are developed. Upon the lower 

 surface there are numerous cliloroplasts in the cells and stomata 

 are present. The latter are formed directly and there is not 

 the cutting off of a subtending cell as is very common in many 

 ferns. The mesophyll consists of about two layers of cells with 

 large lacunae between them. 



Tlie epidermal cells above the midrib are somewhat thickened. 

 The vascular l)undle of the midrib shows a compact mass of 

 tracheary tissue which lies near the upper side of the bundle, 

 so that the bundle approaches the collateral type. Whether 

 any phloem is developed on the upper side of the bundle is 

 not certain. In the smaller veins the collateral nature of the 

 bundle is pronounced as it usually is in the smaller veins of 

 other fern-leaves. New leaves are formed in rapid succession 

 gradually approaching the type of the perfect leaves. In G. 

 pectinata sporangia were noticed upon very small leaves, pro- 

 bably the fourth leaf that was developed upon the young 

 sporophyte (PL X, Fig. 62). 



The structure of the bundles in the mature rhizome and petiole 

 of Ghichenia has been recently studied by Boodle (On the 

 anatomy of Gleicheniaceae, Ann. of Bot., X, Dec. 1901), and 

 the anatomy of the young sporophyte agrees in the main with 

 the older plant. In G. pectinata, according to Boodle, the older 

 rhizome is „solenostelic", i. e. the vascular cylinder is hollow 

 with an outer and inner endodermis and phloem. In the young 

 sporophyte the stele is solid as it is in G. dichotoma. Fig. 131 

 (PI. XIV) shows a transverse section of the first internode of a 

 young sporophyte in which the cotyledon is already developed but 

 the second leaf is still very small. The cortex consists of about 

 six layers of cells of which the innermost forms the not very 

 clearly defined endodermis. Within the latter is the pericycle 

 which is imperfectly two-layered and within this is a layer of 



